Manual 789c - 785c 6t3p4s

Service Training Meeting Guide 706

SESV1706 November 1998

TECHNICAL PRESENTATION

785C/789C OFF-HIGHWAY TRUCKS

785C/789C OFF-HIGHWAY TRUCKS MEETING GUIDE 706

SLIDES AND SCRIPT AUDIENCE

Level II--Service personnel who understand the principles of machine systems operation, diagnostic equipment, and procedures for testing and adjusting.

CONTENT This presentation provides basic maintenance information and describes the systems operation of the engine, power train, steering, hoist and the air system and brakes for the 785C/789C Off-highway Trucks. The Automatic Retarder Control (ARC) and the Traction Control System (TCS) are also discussed.

OBJECTIVES After learning the information in this meeting guide, the serviceman will be able to: 1. locate and identify the major components in the engine, power train, steering, hoist and the air system and brakes; 2. explain the operation of the major components in the systems; and 3. trace the flow of oil or air through the systems.

REFERENCES 784C Tractor/785C Truck Service Manual 784C Tractor/785C Truck Operation and Maintenance Manual 785C Truck with High Altitude Arrangement (HAA) Operation and Maintenance Manual 789C Truck Service Manual 789C Truck Operation and Maintenance Manual Cold Weather Recommendations for Caterpillar Machines Caterpillar Machine Fluids Recommendations

SENR1485 SEBU7173 SEBU7176 SENR1515 SEBU7174 SEBU5898 SEBU6250

PREREQUISITES Interactive Video Course "Fundamentals of Mobile Hydraulics" Interactive Video Course "Fundamentals of Electrical Systems" STMG 546 "Graphic Fluid Power Symbols"

© 1998 Caterpillar Inc.

TEMV9001 TEMV9002 SESV1546

Estimated Time: 24 Hours Visuals: 206 (2 X 2) Slides Serviceman Handouts: 16 Data Sheets Form: SESV1706 Date: 11/98

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SUPPLEMENTAL MATERIAL Reference Manuals Vital Information Management System (VIMS) Service Manual Fluid Power Graphic Symbols 's Guide Flexxaire Fan Installation and Maintenance Manual

SENR6059 SENR3981 SEBC1152

Specification Sheets 785C Off-highway Truck 789C Off-highway Truck 793C Update Off-highway Truck

AEHQ5320 AEHQ5321 AEHQ5186

Salesgrams and Product Bulletins Salesgram "Vital Information Management System (VIMS)" Training Bulletin "Caterpillar Transmission/Drive Train Oil" Product Bulletin "Reporting Particle Count By ISO Code" Salesgram "Caterpillar Extended Life Coolant" Product Data Sheet "Caterpillar Extended Life Coolant" Salesgram "785C/789C/793C Mining Truck Introduction" Salesgram "Cat 769, 771, 773, 775, 777, 785 and 789 Flexxaire Fan Custom Attachment" Product Bulletin "793C Off-highway Truck"

TELQ4478 TEJB1002 PEJT5025 TEKQ0072 PEHP4036 TELQ4459 TELQ4010 TEJB3060

Technical Instruction Modules Vital Information Management System--785B/789B/793B Off-highway Trucks Vital Information Management System--Introduction Electronic Programmable Transmission Control II 769C - 793B Off-highway Trucks--Torque Converter and Transmission Hydraulic Systems 785B/789B/793B Off-highway Trucks--Steering System 769C - 793B Off-highway Trucks--Hoist System 769C - 793B Off-highway Trucks--Air System and Brakes Automatic Retarder Control System Automatic Electronic Traction Aid 769C - 793B Off-highway Trucks--Suspension System

SEGV2610 SEGV2597 SEGV2584 SEGV2591 SEGV2587 SEGV2594 SEGV2595 SEGV2593 SEGV2585 SEGV2599

Service Training Meeting Guides STMG 682 "793C Off-highway Truck" STMG 681 "3500B Engine Controls--Electronic Unit Injection (EUI)" STMG 660 "785B/789B/793B Off-highway Trucks--Maintenance"

SESV1682 SESV1681 SESV1660

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SUPPLEMENTAL MATERIAL (continued) Video Tapes 793C Off-highway Truck--Service Introduction 793C Off-highway Truck--Marketing Introduction Suspension Cylinder Charging Introduction to the Automatic Electronic Traction Aid (AETA) 3500 Engines--EUI Service Introduction Mining Trucks--Cleanliness and Component Life

SEVN4016 AEVN3742 TEVN2155 SEVN9187 SEVN2241 SEVN4142

Booklets Know Your Cooling System Diesel Fuels and Your Engine Oil and Your Engine C-Series Mining Trucks--3500B Diesel Engines Understanding the S•O•S Report

SEBD0518 SEBD0717 SEBD0640 LEDH8400 TEJB1015

Special Instructions Personality Module Booklet--Injectors and Electronic Components Caterpillar Electronic Controls Service Code Information Description List Use of CE Connector Tools Servicing DT Connectors Use of 6V3000 Sure-Seal Repair Kit Use of 8T5200 Signal Generator/Counter Group Suspension Cylinder Servicing Repair of Steering Accumulators Using the 147-5482 Valve Lash Adjustment Group Using 1U5000 Auxiliary Power Unit Using 1U5525 Auxiliary Power Unit Attachments Mining Truck Major Component Removal and Installation Enhancement 785C Assembly Procedure 789C Assembly Procedure

SEHS9914 REHS0126 SEHS9065 SEHS9615 SMHS7531 SEHS8579 SEHS9411 SEHS8757 REHS0128 SEHS8715 SEHS8880 REHS0082 REHS0263 REHS0264

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SUPPLEMENTAL MATERIAL (continued) Brochures Caterpillar Electronic Technician Caterpillar DataView Diesel Engine Oil (CH4) Product Data Sheet How to Take a Good Oil Sample S•O•S Coolant Analysis Air Filter Service Indicator Caterpillar Fully Automatic Transmission Caterpillar Oil-cooled Multiple Disc Brakes Caterpillar Automatic Retarder Control Caterpillar Truck Frames Mining Truck Bodies: Selecting the Right Body System for Your Job C-Series Mining Truck Cabs

NELS1007 NEHP5622 PEHP8038 PEHP6001 PEHP5033 PEHP9013 AEDQ0066 AEDK2546 AEDK0075 AEDK0707 AEDK0083 YEBA3500

Miscellaneous Window Decal "VIMS Keypad Parameters" Pocket Card "Electronic Diagnostic Codes" Chart "Practical Pressure Conversions" Guideline for Reusable Parts "Cleaning Rear Axle Housing Assemblies (785/789)"

SEEU6995 NEEG2500 SEES5677 SEBF8366

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TABLE OF CONTENTS INTRODUCTION ........................................................................................................................7 WALK AROUND INSPECTION...............................................................................................11 OPERATOR'S STATION............................................................................................................45 ENGINE......................................................................................................................................65 Engine Electronic Control System .......................................................................................66 Cooling System.....................................................................................................................88 Lubrication System ...............................................................................................................97 Fuel System.........................................................................................................................101 Air Induction and Exhaust System .....................................................................................106 POWER TRAIN .......................................................................................................................111 Torque Converter ................................................................................................................112 Torque Converter Hydraulic System...................................................................................115 Transmission and Transfer Gears........................................................................................125 Transmission Hydraulic System .........................................................................................128 Differential ..........................................................................................................................138 Final Drives.........................................................................................................................144 Transmission/Chassis Electronic Control System ..............................................................145 STEERING SYSTEM ..............................................................................................................155 HOIST SYSTEM ......................................................................................................................188 AIR SYSTEM AND BRAKES ................................................................................................208 Air Charging System...........................................................................................................210 Brake Systems.....................................................................................................................217 BRAKE ELECTRONIC CONTROL SYSTEM.......................................................................237 Automatic Retarder Control (ARC)....................................................................................240 Traction Control System (TCS) ..........................................................................................245 OPTIONAL EQUIPMENT.......................................................................................................253 FlexxaireTM Fan ...................................................................................................................253 CONCLUSION.........................................................................................................................256 SLIDE LIST..............................................................................................................................257 SERVICEMAN'S HANDOUTS...............................................................................................260

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785C/789C OFF-HIGHWAY TRUCKS

© 1998 Caterpillar Inc.

1 INTRODUCTION • 789C Off-highway Truck

Shown is the 789C Off-highway Truck. The "C" Series trucks are the same as the "B" Series except for the following changes: 3500B engines, improved cab, two different Electronic Control Modules (Transmission/Chassis and Brake) and an electronically controlled hoist. The 789C also has a 40% larger cooling system with a shunt tank located above the radiator.

• Transmission/Chassis Electronic Control System

The second generation Electronic Programmable Transmission Control (EPTC II) has been replaced with the Transmission/Chassis Electronic Control System. The Transmission/Chassis Electronic Control Module (ECM) controls the same functions as the EPTC II plus the hoist and some other functions.

• Brake Electronic Control System

The Automatic Retarder Control (ARC) and the Traction Control System (TCS) control modules have been replaced with one Brake System ECM. The Brake System ECM controls both the ARC and the TCS functions. The TCS is now connected to the CAT Data Link and the Electronic Technician (ET) service tool can be used to diagnose the TCS.

• Load carrying capacity

The load carrying capacities and the Gross Machine Weights (GMW) of the "C" Series trucks are: 785C: 118 to 136 Metric tons (130 to 150 tons) 249480 kg (550000 lb.) GMW 789C: 154 to 177 Metric tons (170 to 195 tons) 317520 kg (700000 lb.) GMW

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• Main system air tank: - Air starting - Service/retarder brakes • Rear hydraulic tank: - Hoist system - Brake system - Torque converter • Front hydraulic tank: - Transmission

Shown is the right side of a 789C truck. The large air tank on the right platform supplies air for starting the truck and for the service and retarder brake system. The hoist, brake and torque converter hydraulic tank (rear) and the transmission hydraulic tank (front) are also visible. The transmission hydraulic system is separate from all the other hydraulic systems.

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• 789C and 793C are similar • 789C has two air filters and vertical ladders • 793C has four air filters and a diagonal ladder • Folded core radiator

Shown is the front of a 789C truck. The 789C is similar in appearance to the 793C and may be difficult to identify from a distance. The 793C can be identified by the four air filters and the diagonal access ladder. The 789C has only two air filters and is equipped with two vertical ladders. The "C" Series trucks use a folded core radiator. The folded core radiator provides the convenience of repairing or replacing smaller individual cores.

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• Truck body options: - 12 degree flat floor - Dual slope

• Internal wear surface • External body components

The truck bodies on "C" Series trucks are mandatory options. Two body styles are available for the "C" Series trucks: - A 12 degree flat floor design that provides uniform load dumping, excellent load retention and a low center of gravity. - A dual-slope design with a "V" bottom main floor to reduce shock loading, center the load and reduce spills. All internal wear surfaces of the truck bodies are made with 400 Brinell hardness steel. All attachment body liners are also made with 400 Brinell hardness steel. The external components of the bodies are made of steel with a yield strength of 6205 bar (90000 psi). The forward two-thirds of the body floor is made with 20 mm (.79 in.) thick 400 Brinell steel plate. The rear one-third of the body floor is made with a 10 mm (.39 in.) thick 400 Brinell sub plate and a 20 mm (.79 in.) thick 400 Brinell body grid liner plate. As an option, the grid liner plate can be made with 500 Brinell steel.

• Rear suspension cylinders

The rear suspension cylinders absorb bending and twisting stresses rather than transmitting them to the main frame.

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785C/789C MAINTENANCE ice 789C Serv re Procedu

WALK AROUND INSPECTION 5 WALK AROUND INSPECTION • Read the Operation and Maintenance Manual

Before working on or operating the truck, read the Operation and Maintenance Manual thoroughly for information on safety, maintenance and operating techniques. Safety Precautions and Warnings are provided in the manual and on the truck. Be sure to identify and understand all symbols before starting the truck. The first step to perform when approaching the truck is to make a thorough walk around inspection. Look around and under the truck for loose or missing bolts, trash build-up and for coolant, fuel or oil leaks. Look for indications of cracks. Pay close attention to high stress areas as shown in the Operation and Maintenance Manual. INSTRUCTOR NOTE: The form numbers for the Operation and Maintenance Manuals are provided under "References" on Page 2.

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10 HOURS/DAILY MAINTENANCE CHECKS BATTERIES

TRANSMISSION OIL LEVEL

STEERING OIL LEVEL

HOIST, CONVERTER AND BRAKE OIL LEVEL

AUTO LUBE RESERVOIR AIR FILTER, RESTRICTION INDICATORS AND PRECLEANERS

SUSPENSION CYLINDER HE REAR AXLE OIL LEVEL

COOLANT LEVEL REAR AXLE AND BRAKE CYLINDER BREATHERS

BELTS AND ETHER CYLINDERS ENGINE OIL LEVEL

FRAME FOR CRACKS AND BODY PADS

WINDSHIELD WASHER LEVEL AND A/C FILTER WASH WINDOWS, CAB FRESH AIR FILTERS, SEAT BELT, INDICATORS, GAUGES, BRAKE TESTS SECONDARY STEERING AND BACK-UP ALARM

AIR RESERVOIR MOISTURE

LEAKS AND TRASH BUILD-UP

TIRE INFLATION PRESSURE

SUSPENSION CYLINDER HEIGHT, GREASE BREATHERS AND WHEEL BREATHERS

FUEL LEVEL AND DRAIN MOISTURE

WHEEL NUTS

6 • Maintenance

The following list identifies the items that must be serviced every 10 Hours or Daily.

- 10 hours/daily

- Walk around inspection: Check for loose or missing bolts, leaks and cracks in frame structures - Suspension cylinders: Measure/recharge - Transmission oil: Check level - Hoist, converter and brake system oil: Check level - Rear axle oil: Check level - Fuel tank: Drain moisture - Engine crankcase oil: Check level - Radiator: Check level and radiator core plugging - Air filters and precleaners: Check restriction indicators and precleaner dirt level - Steering system oil: Check level - Air tanks: Drain moisture - Brakes: Check operation - Indicators and gauges: Test operation - Seat belt: Inspect - Back-up alarm: Test operation - Secondary steering: Test operation

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• Front wheel bearing inspection plug (arrow)

The front wheel bearing oil level is checked and filled by removing the plug (arrow) in the center of the wheel bearing cover. The oil should be level with the bottom of the plug hole.

• Oil change interval 500 hours

The service interval for changing the front wheel bearing oil has been reduced from 2000 hours to 500 hours.

• Use only TDTO oil

Use only Transmission Drive Train Oil (TDTO) with a specification of TO-4 or newer. TDTO TO-4 provides increased lubrication capability for bearings.

• Tire inflation

Check the tire inflation pressure. Operating the truck with the wrong tire inflation pressure can cause heat build-up in the tire and accelerate tire wear. NOTE: Care must be taken to ensure that fluids are contained while performing any inspection, maintenance, testing, adjusting and repair of the machine. Be prepared to collect the fluid in suitable containers before opening any compartment or disassembling any component containing fluids. Refer to the "Tools and Shop Products Guide" (Form NENG2500) for tools and supplies suitable to collect and contain fluids in Caterpillar machines. Dispose of fluids according to local regulations and mandates.

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8 • Front suspension cylinder charge

Check the front suspension cylinders for leaks or structural damage. Check the charge condition of the front suspension cylinders when the truck is empty and on level ground. Measure the charge height of the suspension cylinders and compare the dimension with the dimension that was recorded the last time the cylinders were charged. Recharge the cylinders with oil and nitrogen if necessary.

1. Front wheel bearing axle housing breather

Inspect the condition of the front wheel bearing axle housing breather (1). The breather prevents pressure from building up in the axle housing. Pressure in the axle housing may cause brake cooling oil to leak through the Duo-Cone seals in the wheel brake assemblies.

2. Suspension cylinder grease outlet fittings

Two grease outlet fittings (2) are located on the front of each suspension cylinder. The grease supply line for the Auto Lubrication System is located at the rear of the suspension cylinder. No grease outlet fittings should be located on the same side of the suspension cylinder as the grease fill location. An outlet fitting positioned on the same side of the suspension cylinder as the grease fill location will prevent proper lubrication of the cylinder.

• Make sure grease flows from fittings

Make sure that grease is flowing from the outlet fittings to that the suspension cylinders are being lubricated and that the pressure in the cylinders is not excessive. INSTRUCTOR NOTE: For more detailed information on servicing the suspension system, refer to the Special Instruction "Suspension Cylinder Servicing" (Form SEHS9411) and the Technical Instruction Module "769C - 793B Off-highway Trucks--Suspension System" (Form SEGV2599)

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1. Dust valve

On the 785C truck, an air filter housing and a precleaner are located behind the front wheels on both sides of the truck. Check the dust valves (1) for plugging. If necessary, disconnect the clamp and open the cover for additional cleaning.

• Replace dust valve if not flexible

The dust valve is OPEN when the engine is OFF and closes when the engine is running. The dust valve must be flexible and close when the engine is running or the precleaner will not function properly and the service life of the air filters will be reduced. Replace the rubber dust valve if it becomes hard and brittle.

2. Primary fuel filter/water separator - Drain water

The "C" Series trucks may have the optional primary fuel filters with a water separator (2). Two primary filter/water separators are installed, one on each side of the truck. Open the drain valve at the bottom of each housing to drain the water when required. The drain interval is determined by the humidity of the local climate.

- Replace filter

Replace the filter element in each housing every 500 hours or when restricted. The filter elements are removed from the top of the housings.

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• 3512B engine

• Engine oil S•O•S tap (arrow)

Shown is the right side of the 3512B engine used in the 784C tractor and 785C truck. Engine oil samples can be taken at the Scheduled Oil Sampling (S•O•S) tap (arrow) located in the tube between the engine oil cooler and the engine oil filters.

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11 1. Transmission charging filter 2. Transmission lube filter 3. Torque converter charging filter 4. Transmission S•O•S tap 5. Automatic lubrication injector bank

• Auto lubrication adjustment

Located behind the right front tire is the transmission charging filter (1), the transmission lube filter (2), and the torque converter charging filter (3). Transmission oil samples can be taken at the Scheduled Oil Sampling (S•O•S) tap (4). An oil filter by switch is located on each filter. The transmission oil filter by switches provide input signals to the Transmission/Chassis ECM. The Transmission/Chassis ECM sends the signals to the VIMS, which informs the operator if the filters are restricted. The torque converter charging filter by switch provides an input signal directly to the VIMS. One of the three injector banks (5) for the automatic lubrication system is also in this location. These injectors are adjustable and regulate the quantity of grease that is injected during each cycle. A solenoid air valve provides a controlled air supply for the automatic lubrication system. The solenoid air valve is controlled by the Vital Information Management System (VIMS), which energizes the solenoid ten minutes after the machine is started. The VIMS energizes the solenoid for 75 seconds before it is de-energized. Every 60 minutes thereafter, the VIMS energizes the solenoid for 75 seconds until the machine is stopped (shut down). These settings are adjustable through the VIMS keypad in the cab. INSTRUCTOR NOTE: For more detailed information on servicing the automatic lubrication system, refer to the Service Manual module "Automatic Lubrication System" (Form SENR4724).

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1. Transmission hydraulic tank 2. Hoist, converter and brake hydraulic tank

Shown are the transmission hydraulic tank (1) and the hoist, converter and brake hydraulic tank (2). Both tanks are equipped with oil level sight gauges. The oil level of both hydraulic tanks should first be checked with cold oil and the engine stopped. The level should again be checked with warm oil and the engine running.

3. Lower sight gauge for oil level with raised cylinders

The lower sight gauge (3) on the hoist, converter and brake hydraulic tank can be used to fill the tank when the hoist cylinders are in the RAISED position. When the hoist cylinders are lowered, the hydraulic oil level will increase. After the hoist cylinders are lowered, check the hydraulic tank oil level with the upper sight gauge.

4. Hoist, converter and brake tank breather

Inspect the hoist, converter and brake hydraulic tank breather (4) and the transmission hydraulic tank breather (behind the mud flap) for plugging.

• Transmission tank breather (behind mud flap)

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• Tank refill procedure

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When filling the hydraulic tanks after an oil change, fill the tanks with oil to the FULL COLD mark on the sight gauge. Turn on the engine manual shutdown switch (see Slide No. 25) so the engine will not start. Crank the engine for approximately 15 seconds. The oil level will decrease as oil fills the hydraulic systems. Add more oil to the tanks to raise the oil level to the FULL COLD mark. Crank the engine for an additional 15 seconds. Repeat this step as required until the oil level stabilizes at the FULL COLD mark. Turn off the engine manual shutdown switch and start the engine. Warm the hydraulic oil. Add more oil to the tank as required to raise the oil level to the FULL WARM mark.

• Use only TDTO oil

In both tanks, use only Transmission Drive Train Oil (TDTO) with a specification of TO-4 or newer. TDTO TO-4 oil: - Provides maximum frictional capability required for clutch discs used in the transmission, torque converter and brakes. - Increases rimpull because of reduced slippage. - Increases brake holding capability by reducing brake slippage. - Controls brake chatter. - Provides maximum frictional capability required for gears.

NOTICE Failure to correctly fill the hydraulic tanks after an oil change may cause component damage.

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13 • Final drives • Check magnetic plugs (arrow) for metal

• Use only TDTO oil

The rear axles are equipped with double reduction planetary final drives. The magnetic plug (arrow) should be removed from the final drives at regular intervals and checked for metal particles. For some conditions, checking the magnetic plug is the only way to identify a problem which may exist. Use only Transmission Drive Train Oil (TDTO) with a specification of TO-4 or newer. TDTO TO-4 oil provides: - Maximum frictional capability required for gears. - Increased lubrication capability for bearings.

NOTICE The rear axle housing is a common sump for the differential and both final drives. If a final drive or the differential fails, the other final drive components must also be checked for contamination and then flushed. Failure to completely flush the rear axle housing after a failure can cause a repeat failure within a short time.

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14 1. Differential oil level sight glass

The differential oil level is checked by viewing the oil level sight glass (1). The oil should be level with the bottom of the inspection hole.

2. Rear axle oil level sensors

Two oil level sensors (2) provide input signals to the Brake ECM. The Brake ECM sends the signals to the VIMS, which informs the operator of the rear axle oil level. A rear axle oil filter (3) removes contaminants from the rear axle housing.

3. Rear axle housing oil filter • Rear suspension cylinders

Check the rear suspension cylinders for leaks or structural damage. Check the charge condition of the rear suspension cylinders when the truck is empty and on level ground. Measure the charge height of the suspension cylinders and compare the dimension with the dimension that was recorded the last time the cylinders were charged. Recharge the cylinders with oil and nitrogen if necessary.

4. Automatic lubrication injector bank 5. Rear axle breather

The second of three injector banks (4) for the automatic lubrication system is mounted on the top rear of the differential housing. Above the lubrication injectors is a breather (5) for the rear axle. Inspect the condition of the breather at regular intervals. The breather prevents pressure from building up in the axle housing. Excessive pressure in the axle housing can cause brake cooling oil to leak through the Duo-Cone seals in the wheel brake assemblies. INSTRUCTOR NOTE: For more detailed information on servicing the suspension system, refer to the Special Instruction "Suspension Cylinder Servicing" (Form SEHS9411).

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15

• Cable holds body up

The cable that holds the body up is stored below the rear of the body. Whenever work is to be performed while the body is raised, the safety cable must be connected between the body and the rear hitch to hold the body in the raised position.

WARNING The space between the body and the frame becomes a zero clearance area when the body is lowered. Failure to install the cable can result in injury or death to personnel working in this area. The cable will not hold if the hoist control lever is used to power down the body. Always disconnect the hoist valve cylinder linkage when working below the body.

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16

• Fuel tank • Fuel level sight gauge (arrow) • Fuel information

The fuel tank is located on the left side of the truck. The fuel level sight gauge (arrow) is used to check the fuel level during the walk around inspection. The percentage of sulfur in the fuel will affect the engine oil recommendations. The following is a summary of fuel sulfur and oil recommendations: 1. Use API CH-4 performance oils. 2. With fuel sulfur below 0.5%, any API CH-4 oils will have a sufficient Total Base Number (TBN) for acid neutralization. 3. For fuel sulfur values above 0.5%, the new oil TBN should be a minimum of 10 times the fuel sulfur. 4. When 10 times the fuel sulfur exceeds the oil TBN, reduce the oil change interval to approximately one-half the normal change interval.

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1. Primary fuel filter

The primary fuel filter (1) is mounted on the inner side of the fuel tank.

2. Condensation drain valve

Open the drain valve (2) to remove condensation from the fuel tank.

3. Fuel level sensor

A fuel level sensor (3) is also located on the fuel tank. The fuel level sensor provides input signals to the VIMS which informs the operator of the fuel level.

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1. Parking brake release filter

Located in front of the fuel tank is the parking brake release filter (1) and the torque converter outlet screen (2).

2. Torque converter

An oil filter by switch is located on each housing. The parking brake filter by switch provides an input signal to the Brake ECM and the torque converter outlet screen by switch provides an input signal to the VIMS. The Brake ECM sends the signal to the VIMS, which informs the operator if the filter or screen are restricted.

• Filter by switches

3. 789C rear air dryer

The 789C trucks have two air dryers (3) to accommodate the larger four-cylinder air compressor. Shown is the rear of the two air dryers.

• Automatic lubrication injector bank

The third injector bank for the automatic lubrication system is also located in this area.

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1. Brake cylinder breathers

Inspect the condition of the three breathers (1) (two visible) for the brake cylinders. The third breather is located on the front brake master cylinder behind the cross tube. Oil should not leak from the breathers. Oil leaking from the breathers is an indication that the oil piston seals in the brake cylinder need replacement. Air flow from the breathers during a brake application indicates that the brake cylinder air piston seals need replacement.

2. Brake overstroke switch

If air is in the system or a loss of oil downstream from the cylinders occurs, the piston in the cylinder will overstroke and cause an indicator rod to extend and open the brake overstroke switch (2). The switch provides an input signal to the VIMS, which informs the operator of the condition of the service and retarder brake oil circuit. If an overstroke condition occurs, the problem must be repaired and the indicator rod pushed in to end the warning.

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1. 789C front air dryer

On the 789C truck, the second air dryer (1) is located in front of the left front suspension cylinder. On the 785C truck, the only air dryer is located here.

2. Remote air supply connector

The air system can be charged from a remote air supply through a ground level connector (2) inside the left frame.

3. Engine oil quick fill connector

Engine oil can be added at the quick fill connector (3). Use only Diesel Engine Oil (DEO) with a specification of CF-4 or newer. DEO oil with a CH-4 specification is available and should be used if possible.

• Engine oil (DEO CH-4) - Higher temperature capability - Better soot control - Handles higher sulfur fuels

CH-4 engine oil: - Requires more performance tests than previous oils, such as CE or CF, and has a narrower performance band. - Can withstand higher temperatures before coking and has better dispersing capability for controlling soot. - Has better fuel sulfur neutralization capability.

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2. Engine oil dipstick

The engine oil filters (789C shown) are located on the left side of the engine. Engine oil should be added at the fill tube (1) and checked with the dipstick (2). The 785C has three engine oil filters and is checked and filled through the engine cover (see Slide No. 22).

3. 789C engine oil S•O•S tap

On the 789C truck, engine oil samples can be taken at the Scheduled Oil Sampling (S•O•S) tap (3). (For the 785C truck, see Slide No. 10.)

4. Engine oil pressure sensor

The engine lubrication system is equipped with two oil pressure sensors (4). A sensor is located on each end of the oil filter base. One sensor measures engine oil pressure before the filters. The other sensor measures oil pressure after the filters. The sensors provide input signals to the Engine Electronic Control Module (ECM). The ECM provides input signals to the VIMS, which informs the operator of the engine oil pressure. Together, these sensors inform the operator if the engine oil filters are restricted.

• 789C engine oil filters 1. Engine oil fill tube

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• 785C engine oil filters • Trapped engine oil drain (arrow)

Shown is the 3512B engine used in the 785C truck. Three oil filters are located on the left side of the engine. The 3512B engine also has a fitting (arrow) that can be used to drain the engine oil that is trapped above the filters. Do not add oil through the fitting (arrow) because unfiltered oil will enter the engine. Any contamination could cause damage to the engine.

NOTICE When changing the engine oil filters, drain the engine oil that is trapped above the oil filters through the fitting (arrow) to prevent spilling the oil. Oil added to the engine through the fitting (arrow) will go directly to the main oil galleries without going through the engine oil filters. Adding oil to the engine through the fitting (arrow) may introduce contaminants into the system and cause damage to the engine.

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1. High speed oil change connector

Engine oil can be added through a high speed oil change connector and will enter the oil pan through the fitting (1).

2. Engine oil level switch

An engine oil level switch (2) provides input signals to the Engine ECM. The Engine ECM provides an input signal to the VIMS, which informs the operator of the engine oil level. The oil level switch tells the operator when the engine oil level is low and it is unsafe to operate the truck without causing damage to the engine. The ENG OIL LEVEL LOW message is a Category 2 or 3 Warning.

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• Secondary fuel filters 1. Fuel priming pump 2. Fuel filter by switch

The secondary fuel filters and the fuel priming pump (1) are located above the engine oil filters on the left side of the engine. The fuel priming pump is used to fill the filters after they are changed. A fuel filter by switch (2) is located on the filter base. The by switch provides an input signal to the Engine ECM. The Engine ECM sends the signal to the VIMS, which informs the operator if the filters are restricted. NOTE: If the fuel system requires priming, it may be necessary to block the fuel return line during priming to force the fuel into the injectors.

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25 1. Manual engine shutdown switch

Before climbing the truck ladder, make sure that the manual engine shutdown switch (1) is OFF. The engine will not start if the manual shutdown switch is ON. If necessary, the switch can be used to stop the engine from the ground level. Operate the switch periodically to check the secondary steering system.

2. Engine and access ladder light switches

The toggle switches (2) control the lights in the engine compartment and above the access ladder.

3. RS-232 connector for VIMS

The RS-232 service connector (3) is used to connect a laptop computer with VIMS PC software to new source and configuration files, view real time data or logged information from the VIMS.

4. Battery disconnect switch

The battery disconnect switch (4) and VIMS service connector key switch (5) must be in the ON position before the laptop computer with VIMS software will communicate with the VIMS.

5. Key switch for VIMS service connector 6. VIMS service lamp

The blue service lamp (6) is part of the VIMS. When the key start switch is turned to the ON position, the VIMS runs through a self test. During the self test, the service lamp will flash three times if any logged events are stored in the VIMS main module and once if no logged events are stored. During normal operation, the service lamp will turn ON to notify service personnel that the VIMS has an active data (machine) or maintenance (system) event. The service lamp flashes to indicate when an event is considered abusive to the machine.

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26 • 789C truck • Inspect radiator 1. Air filter restriction indicators 2. Dust valves

Shown is the 789C truck. While climbing the ladder, make a thorough inspection of the radiator. Be sure that no debris or dirt is trapped in the cores. Check the air filter restriction indicators (1) located on both sides of the truck. If the yellow pistons are in the red zone (indicating that the filters are plugged), the air filters must be serviced. Check the dust valves (2) for plugging. If necessary, disconnect the clamp and open the cover for additional cleaning. Replace the dust valve if the rubber is not flexible. The VIMS will also provide the operator with an air filter restriction warning when the filter restriction is approximately 6.2 kPa (25 in. of water). Black exhaust smoke is also an indication of air filter restriction.

• Large primary element • Small secondary element

Two filter elements are installed in the filter housings. The large element is the primary element and the small element is the secondary element. Air intake system tips: - The primary element can be cleaned a maximum of six times. - Never clean the secondary element for reuse. Always replace the secondary element. - Air filter restriction causes black exhaust smoke and low power. - A 0.6°C (1°F) increase in intake temperature increases exhaust temperature 1.8°C (3°F). - For every 250 mm (10 in.) of water restriction above 500 mm (20 in.) of water in an air filter, the inlet temperature increases 60°C (100°F). - Exhaust temperature should not exceed 750°C (1382°F).

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• 789C cooling system capacity increased 1. Engine coolant shunt tank • Engine cooling systems: - Jacket water cooling system - Aftercooler cooling system 2. Coolant level gauges • Use distilled water

• Never use water alone

Shown is a 789C truck. The capacity of the 789C cooling system has been increased by 40% from 474 Liters (125 gal.) to 663 Liters (175 gal.). The radiator is larger and a shunt tank (1) has been added above the radiator. The cooling system on the "C" Series trucks is divided into two systems. The two systems are the jacket water cooling system and the aftercooler cooling system. These two systems are not connected. When servicing the cooling systems, be sure to drain and fill both systems separately. The coolant levels are checked at the shunt tank. Use the gauges (2) on top of the shunt tank to check the two coolant levels. The water used in the cooling system is critical for good cooling system performance. Use distilled or deionized water whenever possible to prevent acids or scale deposits in the cooling system. Acids and scale deposits result from contaminants that are found in most common water sources. Never use water alone. All water is corrosive at engine operating temperatures without coolant additives. Also, water alone has none of the lubrication properties which are required for water pump seals.

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• Trucks are filled with Extended Life Coolant (ELC)

The "C" Series trucks are filled at the factory with Extended Life Coolant (ELC). If ELC is maintained in the radiator, it is not necessary to use a supplemental coolant additive. If more than 10% of conventional coolant is mixed with the ELC, a supplemental coolant additive is required.

• Conventional coolant:

With conventional coolant, maintain a 3 to 6% concentration of supplemental coolant additive. - Too much additive will form insoluble salts that cause water pump seal wear, plugging and will coat parts with excessive deposits that prevent heat transfer. - Not enough additive will result in severe cavitation erosion which will pit and corrode cylinder liner and block surfaces. - Use the 4C9301 Test Kit to measure the concentration of the supplemental coolant additive in the cooling system.

- Maintain 3 to 6% concentration of supplemental coolant additive

• Maintain 30 to 60% antifreeze concentration

Maintain a 30 to 60% concentration of Caterpillar Antifreeze. - More than 60% antifreeze concentration will reduce freeze protection and cause radiator plugging. - Less than 30% antifreeze concentration will result in cavitation erosion, which will pit and corrode cylinder liner and block surfaces and decrease water pump life. - Most commercial antifreezes are formulated with high silicate content for gasoline engines and are not recommended for diesel engines.

• Maintain correct operating temperature

The engine should operate between 88 and 99°C (190 and 210°F). - Operating below this temperature range will cause overcooling problems. - Operating above this temperature range will cause overheating problems.

• Maintain correct cooling system pressure

Cooling system pressure should be between 55 and 110 kPa (8 and 16 psi). - Raising the pressure raises the boiling point. If the pressure is inadequate, the coolant will boil over and the engine will overheat.

• Do not fill cooling system too fast

Do not fill the cooling system faster than 20 L/min. (5 gpm). - Filling the cooling system faster than 20 L/min. (5 gpm) will cause air pockets that could produce damaging steam.

• Adjust fan belts

Keep the fan belts adjusted.

• Keep radiator fins straight and clean

Keep the radiator cooling fins straight and clean.

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1. Air cleaner indicators

Shown is a 785C truck. The air cleaner indicators (1) are located above the radiator next to the air filter screens. If the yellow pistons are in the red zone (indicating that the filters are plugged), the air cleaners must be serviced.

2. Coolant level gauges

The coolant levels are checked at the radiator top tank. Use the gauges (2) on top of the radiator to check the two coolant levels.

• 785C truck

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29

• Ether cylinders (arrow)

The ether cylinders (arrow) are located in the engine compartment behind the radiator. Make sure the ether cylinders are not empty.

• Automatic ether injection

The Engine ECM will automatically inject ether from the ether cylinders during cranking. The duration of automatic ether injection depends on the jacket water coolant temperature. The duration will vary from 10 to 130 seconds.

• Manual ether injection

The operator can also inject ether manually with the ether switch in the cab on the center console (see Slide No. 48). The manual ether injection duration is 5 seconds. Ether will be injected only if the engine coolant temperature is below 10°C (50°F) and engine speed is below 1900 rpm. Ether starting tip: - Cold weather causes rough combustion and white exhaust smoke from unburned fuel. Ether injection will reduce the duration and severity of unburned fuel symptoms.

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30

• Batteries

The batteries are located below the access on the right platform. Inspect the battery connections for corrosion or damage. Keep the battery terminals clean and coated with petroleum jelly. Inspect the electrolyte level in each battery cell, except for maintenance free batteries. Maintain the level to the bottom of the fill openings with distilled water. WARNING Batteries give off flammable fumes that can explode resulting in personal injury. Prevent sparks near batteries. They could cause vapors to explode. Do not allow jumper cable ends to each other or the machine. Do not smoke when checking battery electrolyte levels. Electrolyte is an acid and can cause personal injury if it s skin or eyes. Always wear eye protection when starting a machine with jumper cables. Always connect the battery positive (+) to battery positive (+) and the battery negative (-) to the stalled machine frame (-).

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1. Automatic lubrication tank

Located on the right platform are the automatic lubrication system grease tank (1), the main air system tank (2) and the steering system tank (3).

2. Main air system tank

Check the level of the grease in the automatic lubrication system tank with the grease level indicator located on top of the tank.

3. Steering system tank

A drain valve is located at the bottom right of the main air system tank. Drain the condensation from the air tank each morning.

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1. Steering ENGINE STOPPED oil level

The oil level for the steering system tank is checked at the upper sight gauge (1) when the oil is cold and the engine is stopped. After the engine is started, the oil level will decrease as the oil fills the steering accumulators.

2. Steering ENGINE RUNNING oil level

After the accumulators are filled, the oil level should be checked again at the lower sight gauge (2). When the engine is running and the accumulators are fully charged, the oil level should not be below the ENGINE RUNNING marking of the lower gauge. If the ENGINE RUNNING level is not correct, check the nitrogen charge in each accumulator. A low nitrogen charge will allow excess oil to be stored in the accumulators and will reduce the secondary steering capacity.

3. Steering tank pressure release button

Before removing the cap to add oil to the steering system, be sure that the engine was shut off with the key start switch, and the steering oil has returned to the tank from the accumulators. Then, depress the pressure release button (3) on the breather to release any remaining pressure from the tank.

4. Main steering oil filter

Also located on the tank are the main steering oil filter (4) and the steering pump case drain filter (5).

5. Steering pump case drain filter

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6. APU supplemental steering connector

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If the steering pump fails or if the engine cannot be started, the connector (6) is used to attach an Auxiliary Power Unit (APU). The APU will provide supply oil from the steering tank at the connector (6) to charge the steering accumulators. Steering capability is then available to tow the truck.

INSTRUCTOR NOTE: For more detailed information on servicing the steering accumulators, refer to the Special Instruction "Repair of 4T8719 Bladder Accumulator Group" (Form SEHS8757). For more information on using the APU, refer to the Special Instructions "Using 1U5000 Auxiliary Power Unit (APU)"(Form SEHS8715) and "Using the 1U5525 Attachment Group" (Form SEHS8880).

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33

• Parking/secondary brake air tank drain valve (arrow)

Another small air tank (not visible) is located behind the cab (see Slide No. 178). The air tank behind the cab supplies air to the parking and secondary brakes. Drain the moisture from the tank daily with the drain valve (arrow).

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1. Windshield washer reservoir

The windshield washer reservoir (1) is located in the compartment in front of the cab. Keep the reservoir full of windshield washer fluid.

2. Air conditioner filter

The air conditioner filter (2) is also located in the compartment in front of the cab. Clean or replace the filter element when a reduction of circulation in the cab is noticed.

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35

• 10 hours/daily checks performed in the cab

The remaining 10 Hours or Daily checks are performed in the operator's compartment: -

Brakes: Check operation Indicators and gauges: Test operation Seat belt: Inspect Back-up alarm: Test operation Secondary steering: Test operation

The brakes are checked by engaging one of the brake systems and placing the shift lever in FIRST FORWARD. Accelerate the engine until the truck moves. The truck must not move below 1200 rpm. This procedure should be repeated for each brake lever or pedal. • Cab fresh air filter (arrow)

The cab fresh air filter is located behind the cover (arrow). Clean or replace the cab fresh air filter when necessary. INSTRUCTOR NOTE: Refer to the Operation and Maintenance Manual for more information on the remaining tests performed in the cab.

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36

OPERATOR'S STATION • "C" Series cab resembles "D" Series

The operator's station for the "C" Series Off-highway Trucks has been changed to improve operator comfort and ergonomics. The "C" Series cab now resembles the cab used on the smaller "D" Series Off-highway Trucks.

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• Operator and trainer seats

Shown is a view of the operator's seat and the trainer's seat. The seats are more comfortable with improved seat adjustments. The trainer's seat has more leg room and can be replaced with an attachment air suspension seat.

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38 • Hoist control lever (arrow) • Electronically controlled hoist • Hoist SNUB position

• Hoist lever in FLOAT for normal operation

• Reverse inhibitor operation

The "C" Series truck hoist system is electronically controlled. The hoist control lever (arrow) activates the four positions of the hoist control valve. The four positions are: RAISE, HOLD, FLOAT and LOWER. A fifth position of the hoist valve is called the SNUB position. The operator does not have control over the SNUB position. The body position sensor (see Slide No. 129) controls the SNUB position of the hoist valve. When the body is lowered, just before the body s the frame, the Transmission/Chassis ECM signals the hoist solenoids to move the hoist valve spool to the SNUB position. In the SNUB position, the body float speed is reduced to prevent hard of the body with the frame. The truck should normally be operated with the hoist lever in the FLOAT position. Traveling with the hoist in the FLOAT position will make sure the weight of the body is on the frame and body pads and not on the hoist cylinders. The hoist valve will actually be in the SNUB position. If the transmission is in REVERSE when the body is being raised, the hoist lever sensor is used to shift the transmission to NEUTRAL. The transmission will remain in NEUTRAL until: 1. The hoist lever is moved into the HOLD or FLOAT position; and 2. the shift lever has been cycled into and out of NEUTRAL. NOTE: If the truck is started with the body raised and the hoist lever in FLOAT, the lever must be moved into HOLD and then FLOAT before the body will lower.

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• Left side of dash

Shown is an overall view of the dash from the left side of the cab. Some of the improvements are: -

Telescopic/tilt steering column for individual adjustment Intermittent wiper/washer, turn signal control and dimmer switch Enhanced instrument layout Backlit rocker switches Steering wheel mounted electric horn control

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The operator controls to the left of the steering column are: 1. Steering column adjustment lever 2. Wiper/washer, turn signal and dimmer control 3. Horn control 4. Cigarette lighter

- Telescopic/tilt steering column adjustment lever (1): Push for telescoping and pull for tilt - Intermittent wiper/washer, turn signal control and dimmer switch (2) - Steering wheel mounted electric horn control (3) - Cigarette lighter (4): The cigarette lighter socket receives a 12-Volt power supply. This socket can be used as a power supply for 12-Volt appliances. Another 12-Volt power port is provided behind the operator's seat.

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41

Shown is a closer view of the intermittent wiper/washer, turn signal control and dimmer switch. • Windshield washer

Windshield washer: Push the button at the end of the lever to activate the electrically powered windshield washer.

• Intermittent wiper

Intermittent wiper switch (six positions): - OFF (0) - Intermittent position 1 (one bar) - Intermittent position 2 (two bars) - Intermittent position 3 (three bars) - Low speed continuous wiper (I) - High speed continuous wiper (II)

• Dimmer switch

Dimmer switch: Pull the lever toward the operator for BRIGHT lights, and push the lever away from the operator for DIM lights.

• Turn signals

Turn signals: Lift the lever for a RIGHT turn, and lower the lever for a LEFT turn.

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• Retarder lever

Located on the right side of the steering column is the manual retarder lever. The manual retarder lever is used to modulate engagement of the service brakes on all four wheels. The retarder lever can control the modulation of the service brakes more precisely than the service brake pedal located on the cab floor.

• Key start switch

Located on the dash to the right of the retarder lever are (from left to right):

• Temperature knob • Fan speed switch

- Key start switch - Temperature variable knob - Fan speed switch

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Located on the floor of the cab are: 1. Secondary brake pedal

- Secondary brake pedal (1): Used to modulate application of the parking brakes on all four wheels.

2. Service brake pedal

- Service brake pedal (2): Used to modulate engagement of the service brakes on all four wheels. For more precise modulation of the service brakes, use the manual retarder lever on the right side of the steering column.

3. Throttle pedal

- Throttle pedal (3): A throttle position sensor is attached to the throttle pedal. The throttle position sensor provides the throttle position input signals to the Engine ECM.

• Elevated idle

The Engine ECM provides an elevated engine idle speed of 1300 rpm when the engine oil temperature is below 60°C (140°F). The rpm is gradually reduced to 1000 rpm between 60°C (140°F) and 71°C (160°F). When the temperature is above 71°C (160°F), the engine will idle at LOW IDLE (700 rpm). Increasing the low idle speed helps prevent incomplete combustion and overcooling. To temporarily reduce the elevated idle speed, the operator can release the parking brake or depress the throttle momentarily, and the idle speed will decrease to LOW IDLE for 10 minutes.

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1. Transmission shift lever 2. Parking brake air valve • Top and body up gear limits can be reprogrammed

To the right of the operator's seat is the shift console. Located on the shift console are the transmission shift lever (1) and the parking brake air valve (2). The "C" Series truck transmissions have SIX speeds FORWARD and ONE speed REVERSE. The top gear limit and body up gear limit are programmable through the Transmission/Chassis ECM. The top gear limit can be changed from THIRD to SIXTH. The body up gear limit can be changed from FIRST to THIRD.

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• Overhead switches:

Located in the overhead are several switches:

1. Hazard lights

- Hazard lights (1)

2. Headlights and parking/taillights

- Headlights and parking/taillights (2)

3. Fog lights 4. Back-up lights 5. Front flood/ladder lights

- Fog lights (3) - Back-up lights (4) - Front flood/ladder lights (5)

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• "C" Series trucks use only circuit breakers

Shown is the circuit breaker located behind the operator's seat. The previous "B" Series trucks used fuses to protect many of the electrical circuits. The "C" Series trucks use only circuit breakers to protect the electrical circuits.

1. Power port

A 12-Volt/5 amp power port (1) provides a power supply for 12-Volt appliances, such as a laptop computer.

2. VIMS diagnostic connector

A laptop computer with the VIMS software installed can be connected to the diagnostic connector (2) to obtain diagnostic and production information from the VIMS Electronic Control.

3. CAT Data Link connector

A laptop computer with the Electronic Technician (ET) software installed can be connected to the CAT Data Link connector (3) to obtain diagnostic information and perform programming functions on all the electronic controls.

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47

• Center dash

Shown is the center of the front dash . Eight dash indicators, the four-gauge cluster module and the speedometer/tachometer module are visible.

• Left dash indicators (top to bottom):

The four dash indicators to the left of the four-gauge cluster module are (from top to bottom):

- Left turn - Body up

- Left turn

- Reverse

- Body up: Lights when the body is up. Input is from the body position sensor.

- High beam

- Reverse: Lights when the shift lever switch is in REVERSE. - High beam

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• Right dash indicators (top to bottom):

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The four dash indicators to the right of the speedometer/tachometer module are (from top to bottom):

- Right turn

- Right turn

- Action lamp

- Action lamp: Lights when a Category 2, 2-S or Category 3 Warning is active.

- Retarder - TCS

- Retarder: Lights when the retarder is ENGAGED (Auto or Manual). Flashes rapidly when a fault in the ARC system is detected. - TCS: Lights when the Traction Control System (TCS) is ENGAGED.

• Four-gauge cluster module:

The four systems monitored by the four-gauge cluster module are (top and bottom, left to right):

- Engine coolant temperature

- Engine coolant temperature: Maximum operating temperature is 107°C (225°F).

- Brake oil temperature

- Brake oil temperature: Maximum operating temperature is 121°C (250°F).

- System air pressure - Fuel level

- System air pressure: Minimum operating pressure is 450 kPa (65 psi). - Fuel level: Minimum operating levels are 10% (Category 1) and 5% (Category 2).

• Speed/Tach module:

The three systems monitored by the speedometer/tachometer module are:

- Tachometer

- Tachometer: Displays the engine speed in rpm.

- Ground speed

- Ground speed: Displayed in the left side of the three-digit display area and can be displayed in miles per hour (mph) or kilometers per hour (km/h).

- Actual gear

- Actual gear: Displayed in the right side of the three-digit display area and consists of two digits that show the actual transmission gear that is engaged. The left digit shows the actual gear (such as "1," "2," etc.). The right digit shows the direction selected ("F," "N" or "R").

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48 • Rocker switches (top row):

- Throttle back-up

To the right of the Speedometer/Tachometer Module are several rocker switches. The rocker switches control the following systems: Top row (from left to right) - Throttle back-up: Raises the engine speed to 1300 rpm if the throttle sensor signal is invalid.

- Ether starting aid

- Ether starting aid: Allows the operator to manually inject ether if the engine oil temperature is below 10°C (50°F) and engine speed is below 1900 rpm. The manual ether injection duration is five seconds (see Slides No. 66 and 90).

- ARC

- ARC: Activates the Automatic Retarder Control (ARC) system.

- Brake release/hoist pilot

- Brake release/hoist pilot: Used to release the parking brakes for towing and provide hoist pilot oil to lower the body with a dead engine. The small latch must be pushed UP before the switch can be pushed DOWN.

- TCS test

- TCS test: Tests the Traction Control System (TCS). Use this switch when turning in a tight circle with the engine at LOW IDLE and the transmission in FIRST GEAR. The brakes should ENGAGE and RELEASE repeatedly. The test must be performed while turning in both directions to complete the test.

• Rocker switches (bottom row): - lights - Air conditioning

Bottom row (from left to right) - Lights: Use this switch to DIM the lights - Air Conditioning: Use this switch to turn ON the air conditioner.

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• VIMS

Shown is the Vital Information Management System (VIMS) message center module (1) and the keypad (2).

1. Message center module:

The message center module consists of an alert indicator, a universal gauge and a message display window. The alert indicator flashes when a Category 1, 2, 2-S or 3 Warning is present.

- Alert indicator - Universal gauge - Message display window

The universal gauge displays active or logged data (machine) and maintenance (system) events. The universal gauge will also display the status of a parameter selected for viewing by depressing the GAUGE key on the keypad.

2. Keypad

The message display window shows various types of text information to the operator.

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• VIMS warning categories

The VIMS provides three Warning Categories. The first category requires only operator awareness. The second category states that the operation of the machine and the maintenance procedure of the machine must be changed. The third Warning Category states that the machine must be safely shut down immediately.

• Warning Category 1

Warning Category 1 For a Category 1 Warning, the alert indicator will flash. The universal gauge may display the parameter and a message will appear in the message display window. A Category 1 Warning alerts the operator that a machine system requires attention. The "OK" key on the keypad can be used to acknowledge the warning. Some warnings will be silenced for a predetermined period. After this time period, if the abnormal condition is still present, the warning will reappear.

• Warning Category 2

Warning Category 2 For a Category 2 Warning, the alert indicator and the action lamp will flash. The universal gauge may display the parameter and a message will appear in the message display window. A Category 2 warning alerts the operator that a change in machine operation is required to avoid possible damage to the indicated system. The "OK" key on the keypad can be used to acknowledge the warning. Some warnings will be silenced for a predetermined period. After this time period, if the abnormal condition is still present, the warning will reappear.

• Warning Category 2-S

Warning Category 2-S For a Category 2-S Warning, the alert indicator and the action lamp will flash and a continuous action alarm will sound, which indicate a SEVERE Category 2 Warning. The universal gauge may display the parameter and a message will appear in the message display window. A Category 2-S Warning alerts the operator to immediately change the operation of the machine to avoid possible damage to the indicated system. When the change in operation is made to an acceptable condition, the action alarm will turn off.

• Warning Category 3

Warning Category 3 For a Category 3 Warning, the alert indicator and the action lamp will flash and the action alarm will sound intermittently. The universal gauge may display the parameter and a message will appear in the message display window. A Category 3 Warning alerts the operator that the machine must be safely shut down immediately to avoid damage to the machine or prevent personal injury. Some Category 3 Warnings cannot be stopped by pressing the "OK" key.

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GAUGE CLUSTER MODULE

SERVICE LAMP SERVICE KEY SWITCH

VIMS

VIMS RS-232 PORT

MAIN MODULE

SPEEDOMETER/ TACHOMETER MODULE

12

VIMS SERVICE TOOL AND SOFTWARE

VIMS INTERFACE MODULE

MPH km/h

MESSAGE CENTER MODULE

KEYPAD MODULE

3F

ELECTRONIC TECHNICIAN/ECAP DISPLAY DATA LINK VIMS INTERFACE MODULE

KEYPAD DATA LINK CAT DATA LINK

ENGINE ECM ACTION ALARM ACTION LAMP CAT DATA LINK SENSORS

VITAL INFORMATION MANAGEMENT SYSTEM (VIMS)

SENSORS TRANSMISSION/ CHASSIS ECM

BRAKE ECM (ARC/TCS)

50 • VIMS

The VIMS uses two interface modules to receive input signals from many switches and sensors located around the machine. The VIMS also communicates with other electronic controls on the machine. The VIMS provides the operator and the service technician with a complete look at the current and past conditions of all the systems on the truck.

• TPMS is part of VIMS

If the truck is equipped with the VIMS, the Truck Production Management System (TPMS) is an integral part of the VIMS. Access to the TPMS information is provided through the VIMS message center and keypad modules and a laptop computer with the VIMS PC software installed.

• ET required for programming and diagnostics

The VIMS monitors all the systems on the truck, but ET is used for programming, running diagnostic tests and retrieving logged information from the Engine ECM, the Transmission/Chassis ECM, and the Brake ECM (ARC and TCS).

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1. VIMS main module 2. VIMS interface module No. 1 3. VIMS interface module No. 2 4. Brake ECM 5. Transmission/ Chassis ECM

Located in the compartment at the rear of the cab are the VIMS Main Module (1), the VIMS Interface Module No. 1 (2) and the VIMS Interface Module No. 2 (3). These components make up the "heart" of the VIMS. Also in this location are the Brake ECM (4) and the Transmission/Chassis ECM (5). The Brake ECM controls the Automatic Retarder Control (ARC) system, the Traction Control System (TCS) and rear axle cooling. The Transmission/Chassis ECM controls the shifting of the transmission, torque converter lockup, the hoist system, the neutral-start feature, power train filter and temperature monitoring, and the automatic lubrication feature. All these electronic controls, along with the Engine ECM, communicate with each other on the CAT Data Link. All the information from these controls can be accessed through the VIMS message center or a laptop computer with Electronic Technician (ET) or VIMS PC software.

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• VIMS connector

Shown is a laptop computer with the VIMS PC diagnostic software installed. The laptop computer is connected to the VIMS diagnostic connector. Some of the operations that can be performed with a laptop computer with VIMS PC installed are: - View real time data (similar to the status menu of ET) - View payload data - Start and stop a data logger - Calibrate the payload system - source and configuration files (similar to flash programming other ECM’s with ET) - Assign serial and equipment numbers - Reset onboard date, time and hourmeter - event list, data logger, event recorder, payload data, trend data, cumulative data and histogram data INSTRUCTOR NOTE: For more detailed information on the VIMS, refer to the Service Manual Module "Vital Information Management System (VIMS)" (Form SENR6059).

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• Electronic Technician (ET)

Shown is the 7X1700 Communication Adapter and a laptop computer with the Electronic Technician (ET) diagnostic software installed. The communication adapter is connected to the CAT Data Link diagnostic connector located on the circuit breaker .

• ET must be used with electronic controls

The electronic controls (Transmission/Chassis ECM and Brake ECM) used on the "C" Series trucks no longer have diagnostic windows to access diagnostic information. To perform diagnostic and programming functions with these electronic controls, the service technician must use a laptop computer with ET.

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ENGINE • 3512B and 3516B engines

Shown is the 3516B engine used in the 789C Off-highway Truck. The 789C is equipped with the Caterpillar 3516B quad turbocharged and aftercooled engine. The 785C is equipped with the Caterpillar 3512B twin turbocharged and aftercooled engine. The 785C and 789C engines have increased horsepower.

• Engine power ratings

The engine power ratings for the 785C and 789C trucks are: 785C: gross power--1082 kW (1450 hp) net power--1007 kW (1350 flywheel hp) 789C: gross power--1417 kW (1900 hp) net power--1335 kW (1790 flywheel hp) These engines utilize the Electronic Unit Injection (EUI) system for power, reliability and economy with reduced sound levels and low emissions.

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ENGINE ECM

3500B ELECTRONIC CONTROL SYSTEM COMPONENT DIAGRAM GROUND BOLT

ELECTRONIC UNIT INJECTORS

DISCONNECT SWITCH

MAIN KEY START 15 AMP POWER RELAY SWITCH BREAKER

THROTTLE

24 V

TIMING PROBE CONNECTOR

ENGINE COOLANT TEMPERATURE

OIL LEVEL SWITCH (ADD)

REAR AFTERCOOLER TEMPERATURE

SPEED/TIMING SENSOR

ENGINE OIL PRESSURE (FILTERED)

ENGINE OIL PRESSURE (UNFILTERED)

OIL LEVEL SWITCH (LOW)

ETHER SOLENOID ATMOSPHERIC PRESSURE MANUAL ETHER SWITCH

TURBO OUTLET PRESSURE (BOOST)

THROTTLE OVERRIDE SWITCH GROUND LEVEL SHUTDOWN SWITCH

RIGHT TURBO INLET PRESSURE FUEL FILTER SWITCH

CAT DATA LINK

LEFT TURBO INLET PRESSURE CRANKCASE PRESSURE

RIGHT TURBO EXHAUST

A/C PRESSURE SWITCH

LEFT TURBO EXHAUST FAN CLUTCH SOLENOID FAN

SERVICE TOOL TRANSMISSION/CHASSIS ECM

FAN SPEED SENSOR

EXHAUST WASTEGATE SOLENOID

BRAKE ECM VIMS

ENGINE OIL RENEWAL SOLENOID

SHUTTER SOLENOID PRE-LUBRICATION RELAY COOLANT FLOW SWITCH

55 Engine Electronic Control System • 3500B electronic control system component diagram

Shown is the electronic control system component diagram for the 3500B engines used in the "C" Series trucks. Fuel injection is controlled by the Engine Electronic Control Module (ECM). Many electronic signals are sent to the Engine ECM by sensors, switches and senders. The Engine ECM analyzes these signals and determines when and for how long to energize the injector solenoids. When the injector solenoids are energized determines the timing of the engine. How long the solenoids are energized determines the engine speed.

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• Pull-up Voltage

• Pull-up Voltage test

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The Engine ECM will provide a "Pull-up Voltage" to the signal circuit of most sensors when the ECM senses an OPEN circuit. Frequency sensors do not receive a Pull-up Voltage. The signal circuit is usually Pin C of the 3-pin sensor connectors. The Pull-up Voltage for most sensors is approximately 6.50 Volts, but this value can vary with different electronic controls. Generally, the Pull-up Voltage will be higher than the high value of a sensor's normal range. For example, the normal range of a coolant temperature sensor is 0.4 to 4.6 Volts with temperatures between -40°C and +120°C (-40°F and +248°F). The Pull-up Voltage of 6.50 Volts for this sensor is greater than the normal 4.6 Volts high value. To test for Pull-up Voltage, use a digital multimeter set to "DC Voltage," and use the following procedure (key start switch must be ON): 1. Measure between Pin B (analog or digital return) and Pin C (signal) on the ECM side of a sensor connector before it is disconnected. The voltage that is associated with the current temperature or pressure should be shown. 2. Disconnect the sensor connector while still measuring the voltage between Pins B and C. If the circuit between the ECM and the sensor connector is good, the multimeter will display the Pull-up Voltage.

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56

- Controls fuel injection

Fuel injection and some other systems are controlled by the Engine ECM (arrow) located on top of the engine. Other systems controlled by the Engine ECM include:

- Controls other systems

- Ether injection

- Engine start function

- Engine oil pre-lubrication

- Variable speed fan control

• Engine ECM (arrow)

- Has two 40-pin connectors

• ECM cooled by fuel

• Personality modules and flash files

The Engine ECM has two 40-pin connectors. The connectors are identified as "J1" and "J2." Be sure to identify which connector is the J1 or J2 connector before performing diagnostic tests. The Engine ECM is cooled by fuel. Fuel flows from the fuel transfer pump through the ECM to the secondary fuel filters. Occasionally, Caterpillar will make changes to the internal software (personality module) that controls the performance of the engine. These changes can be performed by physically installing a new personality module, located below the ECM, or by using the WinFlash program that is part of the laptop software program, Electronic Technician (ET). ET is used to diagnose and program the electronic controls used in Off-highway Trucks. If using the WinFlash program, a "flash" file must be obtained from Caterpillar and ed into the existing ECM personality module. The ECM in earlier 3500 engines had one 70-pin connector and cannot be reprogrammed with the WinFlash application in ET. Reprogramming of the earlier ECM requires a replacement of the personality module located behind an access cover on the ECM.

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• Timing calibration connector

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A timing calibration connector is located next to the ECM. If the engine requires timing calibration, a timing calibration sensor (magnetic pickup) is installed in the flywheel housing and connected to the timing calibration connector. Using the Caterpillar ET service tool, timing calibration is performed automatically for the speed/timing sensors. The desired engine speed is set to 800 rpm. This step is performed to avoid instability and ensures that no backlash is present in the timing gears during the calibration process. Timing calibration improves fuel injection accuracy by correcting for any slight tolerances between the crankshaft, timing gears and timing wheel. Timing calibration is normally performed after the following procedures: 1. ECM replacement 2. Speed/timing sensor replacement 3. Timing wheel replacement

INSTRUCTOR NOTE: Some of the engine electronic control system input components are shown during the discussion of other systems. See the following slide numbers: 25. 46. 48. 48. 62. 63. 68. 68. 68. 70. 74. 78. 81. 86. 90. 92.

Engine shutdown switch CAT Data Link connector Throttle back-up switch Manual ether switch Air conditioner compressor pressure switch Engine crankcase pressure sensor Coolant temperature sensor Turbocharger outlet pressure sensor Engine fan speed sensor Engine oil level switch Coolant flow switch Rear aftercooler temperature sensor Engine oil pressure and filter restriction sensors Fuel filter restriction switch Turbocharger inlet pressure sensor Turbocharger temperature sensor

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57

• Atmospheric pressure sensor (arrow)

The atmospheric pressure sensor (arrow) is located adjacent to the Engine ECM. The Engine ECM uses the atmospheric pressure sensor as a reference for calculating boost and air filter restriction.

• High altitude derate

The sensor is also used for derating the engine at high altitudes. The ECM will derate the engine at a rate of 1% per kPa to a maximum of 20%. Derating begins at a specific elevation. The elevation specification can be found in the Technical Marketing Information (TMI) located on the Caterpillar Network. If the Engine ECM detects an atmospheric pressure sensor fault, the ECM will derate the fuel delivery to 20%. If the Engine ECM detects an atmospheric and turbocharger inlet pressure sensor fault at the same time, the ECM will derate the engine to the maximum rate of 40%. The Engine ECM also uses the atmospheric pressure sensor as a reference when calibrating all the pressure sensors.

• Atmospheric pressure sensor signal is DC Volts

• Check atmospheric pressure sensor output signal

The atmospheric pressure sensor is one of the many analog sensors that receive a regulated 5.0 ± .0.5 Volts from the Engine ECM. The atmospheric pressure sensor output signal is a DC Voltage output signal that varies between 0.2 and 4.8 Volts DC with an operating pressure range between 0 and 111 kPa (0 and 15.7 psi). To check the output signal of analog sensors, connect a multimeter between Pins B and C of the sensor connector. Set the meter to read "DC Volts." The DC Voltage output of the atmospheric pressure sensor should be between 0.2 and 4.8 Volts DC.

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1. Engine speed/timing sensor

The engine speed/timing sensor (1) is positioned near the rear of the left camshaft. The sensor signals the speed, direction and position of the camshaft by counting the teeth and measuring the gaps between the teeth on the timing wheel which is mounted on the camshaft.

• No speed/timing sensor signal prevents operation

The engine speed/timing sensor is one of the most important inputs to the Engine ECM. If the Engine ECM does not receive an input signal from the engine speed/timing sensor, the engine will not run.

• Check speed/timing sensor output signal

The engine speed/timing sensor receives a regulated 12.5 ± 1.0 Volts from the Engine ECM. To check the output signal of the speed/timing sensor, connect a multimeter between Pins B and C of the speed/timing sensor connector. Set the meter to read "Frequency." The frequency output of the speed/timing sensor should be approximately: - Cranking: 23 to 40 Hz - Low Idle: 140 Hz - High Idle: 385 Hz

2. Engine speed sensor

A ive (two wire) engine speed sensor (2) is positioned on top of the flywheel housing. The ive speed sensor uses the ing teeth of the flywheel to provide a frequency output. The ive speed sensor sends the engine speed signal to the Transmission/Chassis ECM and the Brake ECM.

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The signal from the ive speed sensor is used for several purposes: - Torque converter lockup clutch slippage monitoring - Transmission clutch slippage monitoring - Automatic Retarder Control (ARC) engine control speed The output signal of the ive speed sensor can also be checked by connecting a multimeter between the two pins of the speed sensor connector and setting the meter to read frequency. NOTE: Turn ON the engine shutdown switch (see Slide No. 25) during the cranking test to prevent the engine from starting. The cranking speed and frequency output will vary depending on weather and machine conditions. When viewing engine speed in the ET status screen, cranking speed should be between 100 and 250 rpm.

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59

• Throttle position sensor (arrow)

The throttle position sensor (arrow) provides the desired throttle position to the Engine ECM. If the Engine ECM detects a fault in the throttle position sensor, the throttle back-up switch (see Slide No. 48) can be used to increase the engine speed to 1300 rpm.

• Throttle position sensor signal is PWM

The throttle position sensor receives a regulated 8.0 ± 0.5 Volts from the Engine ECM. The throttle position sensor output signal is a Pulse Width Modulated (PWM) signal that varies with throttle position and is expressed as a percentage between 0 and 100%.

• Check throttle position sensor output signal

To check the output signal of the throttle position sensor, connect a multimeter between Pins B and C of the throttle position sensor connector. Set the meter to read "Duty Cycle." The duty cycle output of the throttle position sensor should be: - Low Idle: 16 ± 6% - High Idle: 85 ± 4%

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• EUI fuel injector solenoid (arrow)

Shown is the top of a cylinder head with the valve cover removed. The most important output from the Engine ECM is the Electronic Unit Injection (EUI) injector solenoid (arrow). One injector is located in each cylinder head. The engine control analyzes all the inputs and sends a signal to the injector solenoid to control engine timing and speed.

• Engine timing and speed

Engine timing is determined by controlling the start and end time that the injector solenoid is energized. Engine speed is determined by controlling the duration that the injector solenoid is energized.

• E-trim code number identifies injector performance range

3500B injectors are calibrated during manufacturing for precise injection timing and fuel discharge. After the calibration, a four-digit "E-trim" code number is etched on the injector tappet surface. The E-trim code identifies the injector's performance range.

• Trim code numbers are programmed into Engine ECM

• Enter new trim codes during injector service

When the injectors are installed into an engine, the trim code number of each injector is entered into the personality module (software) of the Engine ECM using the ECAP or ET service tool. The software uses the trim code to compensate for the manufacturing variations in the injectors and allows each injector to perform as a nominal injector. When an injector is serviced, the new injector's trim code should be programmed into the Engine ECM. If the new trim code is not entered, the previous injector's characteristics are used. The engine will not be harmed if the new code is not entered, but the engine will not provide peak performance.

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3500B IMPROVEMENTS INPUT SWITCHES AND SENSORS • COOLANT FLOW • REAR AFTERCOOLER TEMPERATURE • ENGINE OIL LEVEL • TURBOCHARGER TEMPERATURE • ENGINE OIL FILTER PRESSURE/RESTRICTION • ENGINE FAN SPEED • FUEL FILTER RESTRICTION • AIR CONDITIONER COMPRESSOR PRESSURE • CRANKCASE PRESSURE

61 • 3500B improvements

• Additional inputs

The 3500B engines have many improvements over the original 3500 engines. Some of the improvements are accomplished by adding additional switch and sensor inputs to the Engine ECM. Adding additional inputs allows the ECM to control the engine more precisely. Additional inputs to the 3500B ECM are: -

-

Coolant flow is monitored (see Slide No. 74). Rear aftercooler temperature is measured (see Slide No. 78). Engine oil level is monitored (see Slide No. 70). Two turbocharger temperature sensors measure exhaust temperatures (see Slide No. 92). Two engine oil pressure sensors are located on the oil filter base to measure oil pressure and oil filter restriction (see Slides No. 81 and 82). Engine fan speed is measured (with variable fan speed attachment). Fuel filter restriction is monitored (see Slide No. 86). Air conditioner compressor pressure is monitored (for variable fan speed control) (see Slide No. 62). Engine crankcase pressure is measured (see Slide No. 63).

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62

• Air conditioner compressor switch (arrow)

An air conditioner compressor switch (arrow) is located at the rear of the air conditioner compressor. If the truck is equipped with the variable fan speed attachment, the air conditioner compressor switch signals the Engine ECM when the air conditioner system is ON. When the air conditioner system is ON, the ECM sets the variable speed fan at MAXIMUM rpm. Disconnecting the air conditioner compressor switch will also signal the ECM to set the fan speed at MAXIMUM rpm.

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63

• Crankcase pressure sensor (arrow)

The crankcase pressure sensor (arrow) is located on the right side of the engine above the engine oil cooler. The crankcase pressure sensor provides an input signal to the Engine ECM. The ECM provides the signal to the VIMS, which informs the operator of the crankcase pressure. High crankcase pressure may be caused by worn piston rings or cylinder liners.

• Crankcase pressure event

If crankcase pressure exceeds 3.6 kPa (.5 psi) or 14.4 inches of water, a high crankcase pressure event will be logged. No factory is required to clear this event.

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3500B IMPROVEMENTS PREVIOUS LOGGED EVENTS • AIR FILTER RESTRICTION • LOW OIL PRESSURE • HIGH COOLANT TEMPERATURE • ENGINE OVERSPEED

64 • Events logged by ECM

• 40% derate with two sensor failures

The 3500B ECM logs the four events of the previous 3500 engine plus some additional events. The four events logged by the 3500 ECM and the 3500B ECM are: Air filter restriction: Greater than 6.25 kPa (25 in. of water). Maximum derate of 20%. If the atmospheric and turbo inlet pressure sensors both fail at the same time, a derate of 40% will occur. Low oil pressure: From less than 44 kPa (6.4 psi) at LOW IDLE to less than 250 kPa (36 psi) at HIGH IDLE. High coolant temperature: Greater than 107°C (226°F). Engine overspeed: Greater than 2200 rpm. NOTE: Factory s are required to clear all the events listed above.

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3500B IMPROVEMENTS ADDITIONAL LOGGED EVENTS • OIL FILTER RESTRICTION

• LOW COOLANT FLOW

• FUEL FILTER RESTRICTION

• DEFINED SHUTDOWN

• HIGH EXHAUST TEMPERATURE

• LOW BOOST PRESSURE

• HIGH AFTERCOOLER TEMPERATURE

• HIGH BOOST PRESSURE

• ENGINE OIL LEVEL LOW

• PRE-LUBE OVERRIDE

• HIGH CRANKCASE PRESSURE

65 • Additional logged events

Additional events logged by the 3500B ECM are: Oil filter restriction: Greater than 70 kPa (10 psi), no factory required. Greater than 200 kPa (29 psi), factory required. Fuel filter restriction: Greater than 138 kPa (20 psi). No factory required. Exhaust temperature high: Greater than 750°C (1382°F). Maximum derate of 20%. Factory required. Aftercooler coolant temperature high: Greater than 107°C (226°F). Factory required. Engine oil level low: No factory required. Crankcase pressure high: Greater than 3.6 kPa (.5 psi) or 14.4 inches of water. No factory required.

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Coolant flow low: Factory required. defined shutdown: The customer has the option of installing systems (fire suppression) that will shut down the engine if desired. If the installed system sends a ground signal to the Engine ECM at Connector J1 Pin 19, a defined shutdown will occur. Factory required. The VIMS will shut down the engine for any of the following conditions: - Engine oil level low - Engine oil pressure low - Engine coolant temperature high - Engine coolant level low - Aftercooler coolant level low The engine will shut down only when the ground speed is zero and the parking brake is ENGAGED. Factory required. Boost pressure low: 35 kPa (5 psi) lower than desired. Maximum derate of 10%. No factory required. Boost pressure high: 20 kPa (3 psi) greater than desired. Maximum derate of 10%. No factory required. Pre-lube override: Override the engine oil pre-lubrication system with the key start switch. Factory required. (see Slide No. 67)

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3500B IMPROVEMENTS SYSTEMS CONTROLLED BY ECM • ETHER INJECTION • RADIATOR SHUTTER CONTROL • COLD MODE • COLD CYLINDER CUTOUT • ENGINE START FUNCTION • ENGINE OIL PRE-LUBRICATION • VARIABLE SPEED FAN CONTROL • ENGINE OIL RENEWAL SYSTEM 66 • Engine ECM controls other systems

The Engine ECM also regulates other systems by energizing solenoids or relays. Some of the other systems controlled by the ECM are:

• Ether injection

Ether Injection: The Engine ECM will automatically inject ether from the ether cylinders during cranking. The duration of automatic ether injection depends on the jacket water coolant temperature. The duration will vary from 10 to 130 seconds. The operator can also inject ether manually with the ether switch in the cab on the center console (see Slide No. 48). The manual ether injection duration is 5 seconds. Ether will be injected only if the engine coolant temperature is below 10°C (50°F) and engine speed is below 1900 rpm.

• Radiator shutter control

Radiator Shutter Control: On trucks that operate in cold weather, shutters can be added in front of the radiator. Installing shutters in front of the radiator allows the engine to warm up to operating temperature quicker. If a truck is equipped with the attachment radiator shutter control, the shutters are controlled by the Engine ECM.

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Cold Mode: The Engine ECM provides an elevated engine idle speed of 1300 rpm when the engine oil temperature is below 60°C (140°F). The rpm is gradually reduced to 1000 rpm between 60°C (140°F) and 71°C (160°F). When the temperature is greater than 71°C (160°F), the engine will operate at low idle (700 rpm). Increasing the low idle speed helps prevent incomplete combustion and overcooling. To temporarily reduce the elevated idle speed, the operator can release the parking brake or depress the throttle momentarily, and the idle speed will decrease to LOW IDLE for 10 minutes.

• Cold cylinder cutout

Cold Cylinder Cutout: The 3500B engine uses a cold cylinder cutout function to: - Reduce white exhaust smoke (unburned fuel) after start-up and during extended idling in cold weather - Minimize the time in Cold Mode - Reduce the use of ether injection. After the engine is started and the automatic ether injection system has stopped injecting ether, the Engine ECM will cut out one cylinder at a time to determine which cylinders are firing. The ECM will disable some of the cylinders that are not firing. The ECM can identify a cylinder which is not firing by monitoring the fuel rate and engine speed during a cylinder cutout. The ECM averages the fuel delivery and analyzes the fuel rate change during a cylinder cutout to determine if the cylinder is firing.

• Engine runs rough during Cold Mode

Disabling some of the cylinders during Cold Mode operation will cause the engine to run rough until the temperature increases above the Cold Mode temperature. This condition is normal, but the operator should be aware it exists to prevent unnecessary complaints.

• Engine start function

Engine Start Function: The Engine Start function is controlled by the Engine ECM and the Transmission/Chassis ECM. The Engine ECM provides signals to the Transmission/Chassis ECM regarding the engine speed and the condition of the engine pre-lubrication system. The Transmission/Chassis ECM will energize the starter relay only when: - The shift lever is in NEUTRAL. - The parking brake is ENGAGED. - The engine speed is zero rpm. - The engine pre-lubrication cycle is complete or turned OFF. NOTE: To protect the starter, the starter is disengaged when the engine rpm is above 300 rpm.

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67 • Engine oil pre-lubrication 1. Pre-lubrication pump relay

2. Pre-lubrication pump

Engine Oil Pre-lubrication: Engine oil pre-lubrication is controlled by the Engine ECM and Transmission/Chassis ECM. The Transmission/Chassis ECM signals the Engine ECM when to energize the pre-lubrication pump relay (1). The Engine ECM signals the Transmission/Chassis ECM to crank the engine when: - Engine oil pressure is 3 kPa (.4 psi) or higher. - The pre-lubrication pump (2) has run for 17 seconds. (If the system times out after 17 seconds, a pre-lubrication time out fault is logged in the Engine ECM.) - The engine has been running in the last two minutes. - Coolant temperature is above 50°C (122°F).

• Pre-lubrication override

The engine oil pre-lubrication system can be byed to allow quick starts. To override the pre-lubrication system, turn the key start switch to the CRANK position for a minimum of two seconds. The Transmission/Chassis ECM will begin the pre-lube cycle. While the prelube cycle is active, turn the key start switch to the OFF position. Within 10 seconds, turn the key start switch back to the CRANK position. The Transmission/Chassis ECM will energize the starter relay.

• Pre-lubrication override event

If the engine oil pre-lubrication system is byed using the above procedure, the Engine ECM will log a pre-lube override event that requires a factory to clear. NOTE: The ECAP and ET can enable or disable the pre-lubrication feature in the Engine ECM.

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• Variable speed fan control: 1. Fan control solenoid valve

Variable Speed Fan Control: If the engine is equipped with a variable speed fan, the Engine ECM regulates the fan speed. Fan speed varies according to the temperature of the engine. The ECM sends a signal to the variable speed fan control solenoid valve (1) and engine oil pressure engages a clutch as needed to change the speed of the fan.

2. Jacket water coolant temperature sensor

The jacket water coolant temperature sensor (2) is located in the jacket water temperature regulator (thermostat) housing. The ECM uses the coolant temperature sensor information as the main parameter to control the fan speed. The aftercooler temperature sensor, air conditioner pressure sensor and brake cooling oil temperature sensors are also used as inputs to determine the required fan speed. A speed sensor (not shown) is located behind the fan pulley and informs the ECM of the current fan speed.

• Fan speed sensor (not shown)

• Fan speed overrides

The variable speed fan feature can be turned off using the ECAP or ET service tool. Turning off the variable speed fan feature will set the fan speed at MAXIMUM rpm. Disconnecting the air conditioning compressor switch will also signal the ECM to set the fan speed at MAXIMUM rpm (see Slide No. 62).

3. Turbo outlet pressure sensor

The turbocharger outlet pressure sensor (3) sends an input signal to the Engine ECM. The ECM compares the value of the turbo outlet pressure sensor with the value of the atmospheric pressure sensor and calculates boost pressure. INSTRUCTOR NOTE: For more information on the variable speed fan, refer to the Service Manual "Variable Speed Fan Clutch" (Form SENR8603).

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• Engine oil renewal system components: 1. Oil filter 2. Oil renewal solenoid 3. Fuel pressure regulator • Oil mixes with fuel in fuel tank

Engine Oil Renewal System: Located on the right side of the engine are the components of the optional engine oil renewal system. Engine oil flows from the engine block through an oil filter (1) to the engine oil renewal solenoid (2). A small amount of oil flows from the engine oil renewal solenoid into the return side of the fuel pressure regulator (3). The engine oil returns to the fuel tank with the return fuel. The engine oil mixes with the fuel in the tank and flows with the fuel to the EUI injectors to be burned. When the engine oil renewal system is used, the operator must pay close attention to the ADD OIL message that the VIMS provides to the operator when makeup oil must be added. The oil does not have to be changed when using the engine oil renewal system. When the engine oil renewal system is used, the engine oil filters, the engine oil renewal system filter, the primary fuel filter and the secondary fuel filters must all be changed at 500 hour intervals.

• Sample engine oil to check soot level

Engine oil samples must be taken regularly to ensure that the soot level of the engine oil is in a safe operating range.

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• Oil injection controlled by Engine ECM • Engine oil renewal system parameters

• Oil renewal adjusted with ECAP or ET

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The ECM regulates the amount of oil that is injected by the engine oil renewal solenoid. Several parameters must be met before the ECM will allow the injection of oil through the engine oil renewal system. The parameters that must be met are: - Fuel position is greater than 10. - Engine rpm is between 1100 and 1850 rpm. - Jacket water temperature is between 63°C (145°F) and 107°C (225°F). - Oil filter differential pressure at high idle with warm oil is less than 70 kPa (10 psi). - Fuel filter differential pressure is less than 140 kPa (20 psi). - Fuel level is greater than 10%. - Engine oil level switches are sending a valid signal to the Engine ECM. - Engine has been running more than five minutes. The engine oil renewal system can be turned ON or OFF with the ECAP or ET service tool. The amount of oil injected can also be adjusted by programming the ECM with the ECAP or ET service tool. The factory setting shown in the service tool is "0" and is equivalent to a 0.5% oil to fuel ratio. The ratio can be changed with the service tool from minus 50 (-50) to plus 50 (+50), which is equivalent to 0.25% to 0.75% oil to fuel ratios. INSTRUCTOR NOTE: The optional Engine Oil Renewal System was not available at first shipment of the 785C and 789C trucks.

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The engine oil level switches (1 and 2) provide input signals to the Engine ECM. The Engine ECM provides a signal to the VIMS, which informs the operator of the engine oil level. 1. Add engine oil level switch

If the truck is equipped with the engine oil renewal system attachment, the upper oil level switch (1) will tell the operator when makeup oil must be added. The ADD ENG OIL message is a Category 1 Warning.

2. Engine oil level low switch

The lower oil level switch (2) will tell the operator when the engine oil level is low and it is unsafe to operate the truck without causing damage to the engine. The ENG OIL LEVEL LOW message is a Category 2 or 3 Warning.

• Low oil level event

If the Engine ECM detects a low oil level condition (oil level below the lower switch), the ECM will log a low oil level event. No factory is required to clear this event.

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71 Cooling System • 789C cooling system capacity increased 1. 789C cooling system shunt tank • Engine cooling systems: - Jacket water cooling system - Aftercooler cooling system

Shown is a 789C truck. The capacity of the 789C cooling system has been increased by 40% from 474 Liters (125 gal.) to 663 Liters (175 gal.). The radiator is larger and a shunt tank (1) has been added above the radiator. The shunt tank provides a positive pressure at the coolant pump inlets to prevent cavitation during high flow conditions. The cooling system is divided into two systems. The two systems are the jacket water cooling system and the aftercooler cooling system. The only connection between these two systems is a small hole in the separator plate in the shunt tank. The small hole in the shunt tank prevents a reduction of coolant from either of the two systems if leakage occurs in one of the separator plates in the radiator top or bottom tank. When servicing the cooling systems, be sure to drain and fill both systems separately.

2. Coolant level gauges

The coolant levels are checked at the shunt tank. Use the gauges (2) on top of the shunt tank to check the coolant level.

3. Coolant level switches

A coolant level switch (3) is located on each side of the shunt tank to monitor the coolant level of both cooling systems (guard removed for viewing switch). The coolant level switches provide input signals to the VIMS, which informs the operator of the engine coolant levels.

4. Pressure relief valves

Pressure relief valves (4) prevent the cooling systems from becoming over pressurized.

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1. Coolant level gauges

Shown is the 785C radiator. The 785C is not equipped with a shunt tank. The coolant levels are checked at the radiator top tank. Use the gauges (1) on the top tank to check the coolant level.

2. Coolant level switches

Two coolant level switches (2) are located on the top tank to monitor the coolant level of both cooling systems. The coolant level switches provide input signals to the VIMS, which informs the operator of the engine coolant levels.

3. Pressure relief valves

Pressure relief valves (3) prevent the cooling systems from becoming over pressurized.

• Jacket water cooling system

The jacket water cooling system uses the cores on the right side of the radiator (approximately 60% of the total capacity). The jacket water cooling system temperature is controlled by temperature regulators (thermostats).

• Aftercooler cooling system

The aftercooler cooling system uses the cores on the left side of the radiator (approximately 40% of the total capacity). The aftercooler cooling system does not have thermostats in the circuit. The coolant flows through the radiator at all times to keep the turbocharged inlet air cool for increased horsepower.

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1. Jacket water pump 2. By tube 3. Jacket water thermostat housing • High coolant temperature event

The jacket water pump (1) is located on the right side of the engine. The pump draws coolant from the by tube (2) until the temperature regulators (thermostats) open. The thermostats are located in the housing (3) at the top of the by tube. When the thermostats are open, coolant flows through the radiator to the water pump inlet. If the jacket water cooling system temperature increases above 107°C (226°F), the Engine ECM will log an event that requires a factory to clear.

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74

• Coolant flow warning switch (arrow)

Coolant flows from the jacket water pump, past the coolant flow warning switch (arrow), and through the various system oil coolers (engine, hoist converter and brake, and the transmission). The coolant flow switch sends an input signal to the Engine ECM. The Engine ECM provides the input signal to the VIMS, which informs the operator of the coolant flow status.

• Low coolant flow event

If the ECM detects a low coolant flow condition, a low coolant flow event will be logged. A factory is required to clear this event.

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1. Engine oil cooler 2. Hoist, converter and brake oil coolers 3. Tube to transmission oil cooler

Shown is the right side of the engine. The engine oil cooler (1) and the hoist, converter and brake oil coolers (2) are visible in this view. Jacket water coolant flows through these coolers and through the tube (3) to the transmission oil cooler. Jacket water coolant flows through the transmission oil cooler, the engine oil cooler and the hoist, converter and brake oil coolers to both sides of the engine cylinder block. Coolant flows through the engine block and through the cylinder heads. From the cylinder heads, the coolant flows to the temperature regulators and either goes directly to the water pump through the by tube or to the radiator (depending on the temperature of the coolant).

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JACKET WATER COOLANT FLOW

THERMOSTAT HOUSING

SHUNT TANK

ENGINE BLOCK

ENGINE OIL COOLER HOIST, CONVERTER AND BRAKE OIL COOLER HOIST, CONVERTER AND BRAKE OIL COOLER TRANSMISSION OIL COOLER

RADIATOR JACKET WATER PUMP

76 • Jacket water cooling circuit

Shown is the jacket water cooling circuit. Coolant flows from the jacket water pump through the coolers to the engine block. Coolant flows through the engine block and the cylinder heads. From the cylinder heads, the coolant flows to the temperature regulators (thermostats) and either goes directly to the water pump through the by tube or to the radiator (depending on the temperature of the coolant). The shunt tank (789C only) increases the cooling capacity and provides a positive pressure at the coolant pump inlet to prevent cavitation during high flow conditions. In this illustration and those that follow, the colors used to identify the various pressures in the systems are: Red Green Red and White Stripes Brown Orange Blue Yellow Purple

- Supply oil/water pressure - Drain or tank oil/water - Reduced supply oil pressure - Lubrication or cooling pressure - Pilot or load sensing signal pressure - Blocked oil - Moving components - Air pressure

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1. Aftercooler water pump 2. 789C shunt tank supply tube 3. Aftercooler circuit coolant tube

The auxiliary (aftercooler) water pump (1) for the aftercooler cooling system is located on the left side of the engine. Coolant enters the aftercooler water pump from the radiator or the shunt tank supply tube (2) on the 789C truck. Coolant flows from the pump to the aftercooler cores through the large tube (3)

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1. Rear aftercooler temperature sensor

• Rear aftercooler temperature event

Located in a tube at the rear of the aftercooler is the rear aftercooler temperature sensor (1). The rear aftercooler temperature sensor provides an input signal to the Engine ECM. The Engine ECM uses the rear aftercooler temperature sensor signal with the jacket water temperature sensor signal, the brake temperature sensor signals (four) and the air conditioner compressor pressure signal to control the variable speed fan attachment. The Engine ECM also provides the input signal to the VIMS, which informs the operator of the aftercooler coolant temperature. If the rear aftercooler temperature increases above 107°C (226°F), the Engine ECM will log an event that requires a factory to clear.

2. Front brake oil cooler

Coolant flows through the aftercooler cores to the front brake oil cooler (2) located at the rear of the engine.

• Aftercooler cooling circuit does not have thermostats

Coolant flows through the front brake oil cooler to the aftercooler section of the radiator. The aftercooler cooling system does not have temperature regulators (thermostats) in the circuit.

3. Front brake oil cooler diverter valve

When the service or retarder brakes are ENGAGED, the front brake oil cooler diverter valve (3) allows brake cooling oil to flow through the front brake oil cooler. Normally, front brake cooling oil is diverted around the cooler and goes directly to the front brakes. Diverting oil around the cooler provides lower temperature aftercooler air during high power demands (when climbing a grade with the brakes RELEASED, for example).

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AFTERCOOLER COOLANT FLOW SHUNT TANK FRONT BRAKE OIL COOLER

AFTERCOOLER

AFTERCOOLER WATER PUMP

RADIATOR

79 • Aftercooler cooling circuit

Shown is the aftercooler cooling circuit. Coolant flows from the aftercooler water pump through the aftercooler. Coolant flows through the aftercooler core to the front brake oil cooler located at the rear of the engine. Coolant then flows through the front brake oil cooler to the aftercooler section of the radiator. The aftercooler cooling circuit does not have temperature regulators (thermostats) in the circuit.

• 789C shunt tank

On the 789C truck, the shunt tank increases the cooling capacity and provides a positive pressure at the aftercooler water pump inlet to prevent cavitation during high flow conditions. The 785C truck does not have a shunt tank.

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Lubrication System • Engine oil pump 1. Engine oil pump relief valve

Shown is the 3512B engine used in the 785C truck. The engine oil pump is located behind the jacket water pump on the right side of the engine. The pump draws oil from the oil pan through a screen. The relief valve (1) for the lubrication system is located on the pump. The engine also has a scavenge pump at the rear of the engine to transfer oil from the rear of the oil pan to the main sump.

2. Engine oil cooler by valve 3. Engine oil cooler 4. 785C engine oil S•O•S tap

Oil flows from the pump through an engine oil cooler by valve (2) to the engine oil cooler (3). The by valve for the engine oil cooler permits oil flow to the system during cold starts when the oil is thick or if the cooler is plugged. On the 3512B engine used in the 785C truck, engine oil samples can be taken at the Scheduled Oil Sampling (S•O•S) tap (4).

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• Engine oil filters

Oil flows from the engine oil cooler to the oil filters on the left side of the engine. The oil flows through the filters and enters the engine cylinder block to clean, cool and lubricate the internal components and the turbochargers.

1. Engine oil fill tube

Engine oil is added at the fill tube (1) and checked with the dipstick (2). A by valve for each filter is located in each oil filter base. Engine oil samples can be taken at the Scheduled Oil Sampling (S•O•S) tap (3) (789C only). (See Slide No. 80 for the 785C S•O•S tap location.)

2. Engine oil dipstick 3. 789C engine oil S•O•S tap 4. Engine oil pressure sensors

• Engine oil pressure event

• Engine oil filter restriction events

The engine has two oil pressure sensors. One sensor is located on each end of the oil filter base. The front sensor measures engine oil pressure before the filters. The rear sensor (4) measures oil pressure after the filters. The sensors send input signals to the Engine ECM. The ECM provides the input signal to the VIMS, which informs the operator of the engine oil pressure. Used together, the two engine oil pressure sensors inform the operator if the engine oil filters are restricted. If the engine oil pressure is less than 44 kPa (6.4 psi) at LOW IDLE to less than 250 kPa (36 psi) at HIGH IDLE, the Engine ECM will log an event that requires a factory to clear. If the oil filter restriction exceeds 70 kPa (10 psi), a low oil filter restriction event will be logged. No factory is required to clear this event. If the oil filter restriction exceeds 200 kPa (29 psi), a high oil filter restriction event will be logged. A factory is required to clear this event.

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82

• 785C engine oil filters • Trapped engine oil drain (arrow)

Shown is the 3512B engine used in the 785C truck. The 3512B engine uses three oil filters located on the left side of the engine. The 3512B engine also has a fitting (arrow) that can be used to drain the engine oil trapped above the filters. Do not add oil through the fitting (arrow) because unfiltered oil will enter the engine. Any contamination could cause damage to the engine.

NOTICE When changing the engine oil filters, drain the engine oil trapped above the oil filters through the fitting (arrow) to prevent spilling the oil. Oil added to the engine through the fitting will go directly to the main oil galleries without going through the engine oil filters. Adding oil to the engine through the fitting may introduce contaminants into the system and cause damage to the engine.

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ENGINE OIL SYSTEM ENGINE BLOCK ENGINE OIL RENEWAL SYSTEM SOLENOID

TO FUEL SYSTEM

SCAVENGE PUMP

BY VALVE ENGINE OIL FILTERS

ENGINE OIL COOLER ENGINE OIL PUMP

83 • Engine oil system

The engine oil pump draws oil from the oil pan through a screen. The engine also has a scavenge pump at the rear of the engine to transfer oil from the rear of the oil pan to the main sump. Oil flows from the pump through an engine oil cooler by valve to the engine oil cooler. The by valve for the engine oil cooler permits oil flow to the system during cold starts when the oil is thick or if the cooler is plugged. Oil flows from the engine oil cooler to the oil filters. The oil flows through the filters and enters the engine cylinder block to clean, cool and lubricate the internal components and the turbochargers.

• Engine oil renewal system

Some trucks are equipped with an engine oil renewal system. Engine oil flows from the engine block through an oil filter to an engine oil renewal system manifold. A small amount of oil flows from the engine oil renewal system manifold into the return side of the fuel pressure regulator. The engine oil returns to the fuel tank with the return fuel (see Slides No. 69 and 70).

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84

Fuel System • Primary fuel filter (arrow)

The fuel tank is located on the left side of the truck. Fuel is pulled from the tank through the fuel heater (not shown), if equipped, and through the primary fuel filter (arrow) by the fuel transfer pump located on the right side of the engine behind the engine oil pump.

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1. Fuel transfer pump 2. Fuel transfer pump by valve

The fuel transfer pump (1) is located behind the engine oil pump. The fuel transfer pump contains a by valve (2) to protect the fuel system components from excessive pressure. The by valve setting is higher than the setting of the fuel pressure regulator (see Slide No. 87). Fuel flows from the transfer pump through the Engine ECM to the secondary fuel filters located on the left side of the engine.

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• Secondary fuel filters 1. Fuel priming pump

The secondary fuel filters and the fuel priming pump (1) are located above the engine oil filters on the left side of the engine. The fuel priming pump is used to fill the filters after they are changed.

2. Fuel filter by switch

Fuel filter restriction is monitored with a fuel filter by switch (2) located on the fuel filter base. The fuel filter by switch provides an input signal to the Engine ECM. The ECM provides a signal to the VIMS, which informs the operator if the secondary fuel filters are restricted.

• Fuel filter restriction event

If fuel filter restriction exceeds 138 kPa (20 psi), a fuel filter restriction event is logged. No factory is required to clear this event.

• Fuel flows to EUI injectors

Fuel flows from the fuel filter base through the Electronic Unit Injection (EUI) fuel injectors (see Slide No. 60), the fuel pressure regulator and then returns to the fuel tank. The injectors receive 4 1/2 times the amount of fuel needed for injection. The extra fuel is used for cooling.

• Extra fuel cools injectors

NOTE: If the fuel system requires priming, it may be necessary to block the fuel return line during priming to force the fuel into the injectors.

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1. Fuel pressure tubes to injectors 2. Fuel pressure regulator

Fuel flows from the fuel filter base through the steel tubes (1) to the EUI fuel injectors. Return fuel from the injectors flows through the fuel pressure regulator (2) before returning to the fuel tank. Fuel pressure is controlled by the fuel pressure regulator. Fuel pressure should be 482 + 138 - 103 kPa (70 + 20 - 15 psi) at Full Load rpm.

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FUEL SYSTEM FUEL PRESSURE REGULATOR ENGINE OIL RENEWAL SYSTEM SOLENOID

CYLINDER HEAD

ENGINE BLOCK

SECONDARY FUEL FILTERS

FUEL TANK

PRIMARY FUEL FILTER

FUEL TRANSFER PUMP

ENGINE ECM

FUEL HEATER

88 • Fuel system circuit

Fuel is pulled from the tank through a fuel heater, if equipped, and sent through the primary fuel filter by the fuel transfer pump. Fuel flows from the transfer pump through the Engine ECM to the secondary fuel filters. Fuel flows from the fuel filter base through the fuel injectors in the cylinder heads. Return fuel from the injectors flows through the fuel pressure regulator before returning through the fuel heater to the tank. If equipped with the engine oil renewal system, engine oil flows from the engine block through an oil filter to the engine oil renewal system manifold. A small amount of oil flows from the engine oil renewal system manifold into the return side of the fuel pressure regulator. The engine oil returns to the fuel tank with the return fuel. The engine oil mixes with the fuel in the tank and flows with the fuel to the injectors to be burned.

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Air Induction and Exhaust System • 789C truck 1. Air filter restriction indicators

2. Dust valves

The engine receives clean air through the air filters located on the front of the truck (789C) or on either side of the engine (785C). Any restriction caused by plugged filters can be checked at the filter restriction indicators (1). If the yellow piston is in the red zone, the filters must be cleaned or replaced. Check the dust valves (2) for plugging. If necessary, disconnect the clamp and open the cover for additional cleaning. The dust valve is OPEN when the engine is OFF and closes when the engine is running. The dust valve must be flexible and close when the engine is running or the precleaner will not function properly and the air filters will have a shortened life. Replace the rubber dust valve if it becomes hard and not flexible. The VIMS will also provide the operator with an air filter restriction warning when the filter restriction is approximately 6.2 kPa (25 in. of water). Black exhaust smoke is also an indication of air filter restriction.

• Large primary element • Small secondary element

Two filter elements are installed in the filter housings. The large element is the primary element and the small element is the secondary element.

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1. Turbocharger inlet pressure sensor

The turbocharger inlet pressure sensor (1) is located in a tube between the air filters and the turbochargers. The Engine ECM uses the turbocharger inlet pressure sensor in combination with the atmospheric pressure sensor to determine air filter restriction. The ECM provides the input signal to the VIMS, which informs the operator of the air filter restriction.

• Air filter restriction event

If air filter restriction exceeds 6.25 kPa (25 in. of water), an air filter restriction event will be logged, and the ECM will derate the fuel delivery (maximum derating of 20%) to prevent excessive exhaust temperatures. A factory is required to clear this event. If the Engine ECM detects a turbocharger inlet pressure sensor fault, the ECM will derate the engine to the maximum rate of 20%. If the Engine ECM detects a turbocharger inlet and atmospheric pressure sensor fault at the same time, the ECM will derate the engine to the maximum rate of 40%.

2. Ether cylinders

The Engine ECM will automatically inject ether from the ether cylinders (2) during cranking. The duration of automatic ether injection depends on the jacket water coolant temperature. The duration will vary from 10 to 130 seconds. The operator can also inject ether manually with the ether switch in the cab on the center console (see Slide No. 48). The manual ether injection duration is 5 seconds. Ether will be injected only if the engine coolant temperature is below 10°C (50°F) and engine speed is below 1900 rpm.

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91

• 3516B has four turbochargers (arrows)

Shown is the 3516B engine used in the 789C truck. The 3516B engine is equipped with four turbochargers (arrows). The 785C truck has a 3512B engine with two turbochargers.

• 3512B has two turbochargers

The turbochargers are driven by the exhaust gas from the cylinders which enters the turbine side of the turbochargers. The exhaust gas flows through the turbochargers, the exhaust piping, and the mufflers. The clean air from the filters enters the compressor side of the turbochargers. The compressed air from the turbochargers flows to the aftercoolers. After the air is cooled by the aftercoolers, the air flows to the cylinders and combines with the fuel for combustion.

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92

• Exhaust temperature sensor (arrow)

An exhaust temperature sensor (arrow) is located in each exhaust manifold before the turbochargers. The two exhaust temperature sensors provide input signals to the Engine ECM. The ECM provides the input signal to the VIMS, which informs the operator of the exhaust temperature.

• Causes of high exhaust temperature

Some causes of high exhaust temperature may be faulty injectors, plugged air filters, or a restriction in the turbochargers or the muffler.

• High exhaust temperature derates engine and logs event

If the exhaust temperature is above 750°C (1382°F), the Engine ECM will derate the fuel delivery to prevent excessive exhaust temperatures. The ECM will derate the engine by 2% for each 30 second interval that the exhaust temperature is above 750°C (1382°F) (maximum derate of 20%). The ECM will also log an event that requires a factory to clear.

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FROM AIR FILTERS

3512B AIR INDUCTION AND EXHAUST SYSTEM

MUFFLER

AFTERCOOLER

FROM AIR FILTERS

93 • Air induction and exhaust system

This schematic shows the flow through the air induction and exhaust system. The turbochargers are driven by the exhaust gas from the cylinders which enters the turbine side of the turbochargers. The exhaust gas flows through the turbochargers, the exhaust piping, and the mufflers. The clean air from the filters enters the compressor side of the turbochargers. The compressed air from the turbochargers flows to the aftercoolers. After the air is cooled by the aftercoolers, the air flows to the cylinders and combines with the fuel for combustion.

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POWER TRAIN 785C

94 • Power train components: - Torque converter - Transfer gears - Transmission - Differential - Final drives

POWER TRAIN Power flows from the engine to the rear wheels through the power train. The components of the power train are: -

Torque converter Transfer gears Transmission Differential Final drives

INSTRUCTOR NOTE: In this section of the presentation, component locations and a brief description of the component functions are provided. For more detailed information on the torque converter and ICM (Individual Clutch Modulation) transmission, refer to the Technical Instruction Module "769C - 793B Off-highway Trucks-Torque Converter and Transmission Hydraulic System" (Form SEGV2591).

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Torque Converter • Torque converter: - Provides a fluid coupling - Multiplies torque - Provides direct drive operation

1. Inlet relief valve

The first component in the power train is the torque converter. The torque converter provides a fluid coupling that permits the engine to continue running with the truck stopped. In converter drive, the torque converter multiplies engine torque to the transmission. At higher ground speeds, a lockup clutch engages to provide direct drive. The NEUTRAL and REVERSE ranges are converter drive only. FIRST SPEED is converter drive at low ground speed and direct drive at high ground speed. SECOND through SIXTH SPEEDS are direct drive only. The torque converter goes to converter drive between each shift (during clutch engagement) to provide smooth shifts. Mounted on the torque converter are the inlet relief valve (1), the outlet relief valve (2) and the torque converter lockup clutch control valve (3).

2. Outlet relief valve 3. Lockup clutch control valve 4. Outlet temperature sensor 5. COS sensor

A torque converter outlet temperature sensor (4) provides an input signal to the Transmission/Chassis ECM. The Transmission/Chassis ECM sends the signal to VIMS, which informs the operator of the torque converter outlet temperature. A Converter Output Speed (COS) sensor (5) sends an input signal to the Transmission/Chassis ECM. The Transmission/Chassis ECM sends the signal to the VIMS. The VIMS uses the signal to calculate if any slippage exists in the torque converter lockup clutch or any of the transmission clutches.

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LOCKUP PISTON

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TURBINE

IMPELLER

TORQUE CONVERTER STATOR

CONVERTER DRIVE

TORQUE CONVERTER INLET OIL

FREEWHEEL ASSEMBLY

TORQUE CONVERTER LOCKUP OIL AGE

96 • CONVERTER DRIVE - Output shaft rotates slower than engine rpm - Torque is increased • Torque converter components: - Lockup clutch - Impeller - Turbine - Stator

This sectional view shows a torque converter in CONVERTER DRIVE. The lockup clutch (yellow piston and blue discs) is not engaged. During operation, the rotating housing and impeller (red) can rotate faster than the turbine (blue). The stator (green) remains stationary and multiplies the torque transfer between the impeller and the turbine. The output shaft rotates slower than the engine crankshaft, but with increased torque.

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LOCKUP PISTON

TURBINE

IMPELLER

TORQUE CONVERTER DIRECT DRIVE STATOR TORQUE CONVERTER INLET OIL

STATOR

FREEWHEEL ASSEMBLY

TORQUE CONVERTER LOCKUP OIL AGE

97 • DIRECT DRIVE - Lockup clutch engaged - Output shaft rotates at engine rpm - Stator freewheels

In DIRECT DRIVE, the lockup clutch is engaged by hydraulic pressure and locks the turbine to the impeller. The housing, impeller, turbine, and output shaft then rotate as a unit at engine rpm. The stator, which is mounted on a freewheel assembly, is driven by the force of the oil in the housing and will freewheel at approximately the same rpm.

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Torque Converter Hydraulic System • Torque converter pump has three or four sections: 1. Torque converter scavenge 2. Torque converter charging 3. Parking brake release 4. Rear brake oil cooling (789C only) 5. Torque converter scavenge screen cover

The three (785C) or four (789C) section torque converter pump is located at the bottom rear of the torque converter. The four sections (from the front to the rear) are: -

Torque converter scavenge (1) Torque converter charging (2) Parking brake release (3) Rear brake oil cooling (4) (789C only)

Excess oil that accumulates in the bottom of the torque converter is scavenged by the first section of the pump through a screen behind the access cover (5) and returned to the hydraulic tank.

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1. Torque converter charging filter

Oil flows from the torque converter charging section of the pump to the torque converter charging filter (1).

2. Torque converter charging filter by switch

An oil filter by switch (2) is located on the torque converter charging filter. The oil filter by switch provides an input signal to the VIMS, which informs the operator if the filter is restricted.

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1. Torque converter inlet relief valve

Oil flows from the torque converter charging filter to the torque converter inlet relief valve (1). The inlet relief valve limits the maximum pressure of the supply oil to the torque converter. The torque converter inlet relief pressure can be measured at this valve by removing a plug and installing a pressure tap. Inlet relief pressure should not exceed 930 ± 35 kPa (135 ± 5 psi) at high idle when the oil is cold. Normally, the inlet relief pressure will be slightly higher than the outlet relief valve pressure. Oil flows through the inlet relief valve and enters the torque converter.

2. Torque converter outlet relief valve 3. Torque converter outlet relief pressure tap

Some of the oil will leak through the torque converter to the bottom of the housing to be scavenged. Most of the oil in the torque converter is used to provide a fluid coupling and flows through the torque converter outlet relief valve (2). The outlet relief valve maintains the minimum pressure inside the torque converter. The main function of the outlet relief valve is to keep the torque converter full of oil to prevent cavitation. The outlet relief pressure can be measured at the tap (3) on the outlet relief valve. The outlet relief pressure should be: 785C: 345 to 585 kPa (50 to 85 psi) at 1640 ± 65 rpm (TC Stall) 789C: 345 to 585 kPa (50 to 85 psi) at 1715 ± 65 rpm (TC Stall)

4. Torque converter outlet temperature sensor

A torque converter outlet temperature sensor (4) provides an input signal to the Transmission/Chassis ECM. The Transmission/Chassis ECM sends a signal to VIMS, which informs the operator of the torque converter outlet temperature.

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1. Torque converter outlet screen

Most of the oil from the torque converter outlet relief valve flows through the torque converter outlet screen (1) located outside the left frame.

2. Torque converter outlet screen by switch

A torque converter outlet screen by switch (2) provides an input signal to the VIMS, which informs the operator if the torque converter outlet screen is restricted. Oil flows from the torque converter outlet screen to the front brake oil cooler located behind the engine.

3. Parking brake release filter

Oil flows from the parking brake release section of the torque converter pump to the parking brake release filter (3).

4. Parking brake release filter by switch

A parking brake release filter by switch (4) is located on the parking brake release filter. The by switch provides an input signal to the Brake ECM. The Brake ECM sends a signal to VIMS, which informs the operator if the parking brake release filter is restricted.

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1. Front brake oil cooler diverter valve 2. Front brake oil cooler

The oil from the torque converter outlet screen flows through a diverter valve (1) before flowing through the front brake oil cooler (2). When the retarder or service brakes are ENGAGED, the oil is diverted through the cooler to the brakes. When the brakes are RELEASED, the oil byes the cooler and flows directly to the brakes. Diverting oil around the cooler provides lower temperature aftercooler air during high power demands (when climbing a grade with the brakes RELEASED, for example).

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1. Parking brake release valve

Oil from the parking brake release filter flows to the parking brake release valve (1). The parking brake release section of the torque converter pump provides supply oil for several purposes: -

Release the parking brakes Engage the torque converter lockup clutch Hoist valve pilot oil Front (789C) or rear (785C) brake oil cooling

2. Parking brake relief

The parking brake relief valve (2) controls the pressure for parking brake release, torque converter lockup and hoist valve pilot oil. The parking brake release pressure is 4700 ± 200 kPa (680 ± 30 psi).

• Most oil used for brake cooling

Most of the oil from the parking brake release valve flows to the front brake oil cooler on the 789C truck and to the rear brake oil coolers on the 785C truck.

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1. Torque converter lockup clutch valve supply port 2. Torque converter lockup clutch signal oil supply hose

3. Torque converter lockup clutch pressure tap • Do not test converter lockup pressure below 1300 rpm 4. Converter output speed sensor

• Clutch slippage is recorded in VIMS

The parking brake release pump supplies oil to the torque converter lockup clutch valve through the inlet port (1). When the lockup clutch solenoid (located on the transmission housing) is energized by the Transmission/Chassis ECM, transmission pump supply oil (signal oil) enters the lockup valve through the center hose (2). The signal oil pressure is approximately 1725 kPa (250 psi). The signal oil causes the lockup valve to start the modulation process for torque converter lockup. The lockup clutch valve then supplies oil to ENGAGE the lockup clutch in the torque converter. Torque converter lockup clutch pressure can be measured at the tap (3). Torque converter lockup clutch pressure should be 2135 ± 70 kPa (310 ± 10 psi) at 1300 rpm or higher. Do not check the torque converter lockup clutch pressure below 1300 rpm. The Converter Output Speed (COS) sensor (4) sends an input signal to the Transmission/Chassis ECM. The Transmission/Chassis ECM memory also contains the engine rpm and the Transmission Output Speed (TOS) for each gear of the transmission. The Transmission/Chassis ECM provides all of these input signals to the VIMS. Using the information from the Transmission/Chassis ECM, the VIMS calculates if any slippage exists in the torque converter lockup clutch or any transmission clutches and stores this information in the VIMS main module. This information can be ed from the VIMS with a laptop computer.

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TORQUE CONVERTER LOCKUP CLUTCH CONTROL DIRECT DRIVE LOCKUP CLUTCH PILOT PRESSURE (RV) SIGNAL OIL SELECTOR PISTON

LOCKUP SOLENOID

LOCKUP MODULATION VALVE TO LOCKUP CLUTCH (LU)

TO TRANSMISSION LUBE

FROM TRANSMISSION CHARGE PUMP

LOCKUP REDUCING VALVE

TO STATION "D"

SHUTTLE VALVE RELAY VALVE

FROM PARKING BRAKE RELEASE PUMP (PMP)

105 • Lockup clutch valve operation

Shown is a sectional view of the torque converter lockup clutch valve in DIRECT DRIVE. Supply oil from the parking brake release pump is used to provide lockup clutch oil.

• Supply pressure is reduced to pilot pressure

First, supply pressure is reduced to provide pilot pressure to the relay valve. Supply oil to the pressure reduction valve flows through crossdrilled orifices in the spool, past a check valve and enters the slug chamber. The check valve dampens spool movement and reduces the possibility of valve chatter and pressure fluctuation. Oil pressure moves the slug in the right end of the spool to the right and the spool moves to the left against the spring force. The slug reduces the effective area on which the oil pressure can push. Because of the reduced effective area, a smaller, more sensitive spring can be used. Pilot pressure will be equal to the force of the spring on the left end of the spool. The spring force can be adjusted with shims. Pilot pressure is 1725 ± 70 kPa (250 ± 10 psi).

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• Lockup clutch at primary pressure

• Lockup clutch at maximum pressure

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When the lockup solenoid is energized, transmission pump supply (signal) pressure is directed to the relay valve. Before moving the selector piston, the pilot oil moves a shuttle valve to the right, which closes the lower left drain age and opens the check valve. Oil then flows to the selector piston. Moving the selector piston blocks the upper drain age, and the load piston springs are compressed. When the solenoid is energized, supply oil from the parking brake release pump is reduced to provide the lockup clutch pressure. Lockup clutch pressure depends mainly on the force of the load piston valve springs. When the solenoid is energized, pilot oil moves the selector piston down against a stop. When the load piston that compresses the springs is at the top against the selector piston, lockup clutch pressure is at its lowest controlled value. This value is called "primary pressure." As the load piston moves down, lockup clutch pressure increases gradually until the load piston stops. Maximum lockup clutch pressure is then reached. The gradual increase in pressure, which depends on how fast the load piston moves, is called "modulation."

• Load piston orifice determines modulation time

The speed of the load piston movement depends on how fast the oil can flow to the area above the load piston. The load piston orifice meters the flow of oil to the load piston chamber and determines the modulation time.

• Primary pressure is adjusted with shims

Primary pressure is adjusted with shims in the load piston. Final lockup clutch pressure is not adjustable. If the primary pressure is correct and final lockup clutch pressure is incorrect, the load piston should be checked to make sure that it moves freely in the selector piston. If the load piston moves freely, the load piston springs should be replaced.

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TORQUE CONVERTER HYDRAULIC SYSTEM

FRONT BRAKES

REAR BRAKES

TO HOIST SOLENOID MANIFOLD

TORQUE CONVERTER CHARGING FILTER OUTLET RELIEF VALVE

FRONT BRAKE OIL COOLER

CONVERTER LOCKUP VALVE

INLET RELIEF VALVE DIVERTER VALVE

PARKING BRAKE RELEASE VALVE

REAR BRAKE OIL COOLERS CONVERTER OUTLET SCREEN

PARKING BRAKE FILTER

CONVERTER SCAVENGE SCREEN

106 • 789C torque converter hydraulic system

This schematic shows the flow of oil from the torque converter pump through the torque converter hydraulic system on the 789C truck.

• Scavenge pump section

The scavenge pump section pulls oil through a screen from the torque converter housing and sends the oil to the hydraulic tank.

• Charging pump section

The charging pump section sends oil through the torque converter charging filter to the torque converter inlet relief valve. Oil flows from the inlet relief valve through the torque converter to the outlet relief valve. Oil flows from the outlet relief valve through the converter outlet filter and the front brake oil cooler to the front brakes.

• Parking brake release pump section

The parking brake release pump section sends oil through the parking brake release filter to the parking brake release valve and the torque converter lockup clutch valve. Most of the oil flows through the parking brake release valve and the front brake oil cooler to the front brakes.

• 789C rear brake cooling pump section

The brake cooling pump section of the torque converter pump (789C only) sends oil through the two oil coolers located on the right side of the engine to the rear brakes.

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107

Transmission and Transfer Gears 1. Transfer gears 2. Transmission 3. Differential

Power flows from the torque converter through a drive shaft to the transfer gears (1). The transfer gears are splined to the transmission input shaft. The transmission (2) is located between the transfer gears and the differential (3). The transmission is electronically controlled and hydraulically operated as in all other ICM (Individual Clutch Modulation) transmissions in Caterpillar rigid frame trucks. The differential is located in the rear axle housing behind the transmission. Power from the transmission flows through the differential and is divided equally to the final drives in the rear wheels. The final drives are double reduction planetaries.

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108

1. Transmission lube supply hose

Oil flows from the transmission oil cooler to the transfer gears through a hose (1). Transmission lube oil flows through the transfer gears and the transmission to cool and lubricate the internal components.

2. Transmission lube oil pressure tap

The transmission lube pressure relief valve is in the transmission case near the transmission hydraulic control valve. The relief valve limits the maximum pressure in the transmission lube circuit. Transmission lube oil pressure can be measured at the tap (2). At HIGH IDLE, the transmission lube pressure should be 140 to 205 kPa (20 to 30 psi). At LOW IDLE, the transmission lube pressure should be a minimum of 4 kPa (.6 psi).

3. Transmission output speed sensor

The Transmission Output Speed (TOS) sensor (3) is located on the front of the transfer gears. A small shaft runs from the speed sensor location through the entire length of the transmission and engages the transmission output shaft. The transmission speed sensor signal serves many purposes. Some of the purposes are: -

Transmission automatic shifting Speedometer operation Traction Control System (TCS) top speed limit Truck Production Management System (TPMS) distance calculations - Machine speed input to VIMS to determine some warning categories

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POWER SHIFT PLANETARY TRANSMISSION

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109 • Transmission is power shift planetary design

The transmission is a power shift planetary design which contains six hydraulically engaged clutches. The transmission provides six FORWARD speeds and one REVERSE speed.

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Transmission Hydraulic System The transmission pump pulls oil through a suction screen from the transmission tank (see Slides No. 12 and 159) located on the right side of the truck. • Transmission three section pump: 1. Transmission scavenge 2. Transmission lube 3. Transmission charging

The three section transmission pump is mounted on the rear of the pump drive, which is located inside the right frame near the torque converter. The three sections are: - Transmission scavenge (1) - Transmission lube (2) - Transmission charging (3) The transmission scavenge section pulls oil through the magnetic screens located at the bottom of the transmission. The scavenged oil from the transmission is sent to the transmission tank.

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111

• Transmission magnetic scavenge screens (arrow)

Shown is the location of the transmission magnetic scavenge screens (arrow). These screens should always be checked for debris if a problem with the transmission is suspected. Oil is scavenged from the transmission by the first section of the transmission pump (see Slide No. 110).

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112 1. Transmission charging filter

Oil flows from the charging section of the transmission pump to the transmission charging filter (1) located on the frame behind the right front tire.

2. Transmission oil temperature sensor

Oil flows from the transmission charging filter to the transmission control valve located on top of the transmission. A transmission oil temperature sensor (2) is located in the tube between the transmission charging filter and the transmission control valve. The temperature sensor provides an input signal to the Transmission/Chassis ECM. The Transmission/Chassis ECM sends a signal to VIMS, which informs the operator of the transmission oil temperature.

3. Transmission lube filter

Oil flows from the lube section of the transmission pump to the transmission lube filter (3). Oil flows from the transmission lube filter through the transmission oil cooler to the transfer gears. Transmission lube oil flows through the transfer gears and the transmission to cool and lubricate the internal components.

• Oil filter by switches

An oil filter by switch is located on each filter. The oil filter by switches provide input signals to the Transmission/Chassis ECM. The Transmission/Chassis ECM sends signals to the VIMS, which informs the operator if the filters are restricted.

4. Transmission S•O•S tap

Transmission oil samples can be taken at the Scheduled Oil Sampling (S•O•S) tap (4).

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1. Transmission oil cooler by valve 2. Transmission oil cooler

Oil flows from the transmission lube filter and the transmission control valve through the transmission oil cooler by valve (1) to the transmission oil cooler (2). The by valve for the transmission oil cooler permits oil flow to the system during cold starts when the oil is thick or if the cooler is restricted. Oil flows from the transmission oil cooler to the transfer gears and the transmission to cool and lubricate the internal components.

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114

1. Transmission control valve supply port 2. Transmission charging oil return port 3. Torque converter lockup clutch solenoid 4. Lockup clutch signal oil hose 5. Transmission charging pressure tap

The transmission charging pump supplies oil to the transmission hydraulic control valve and the shift solenoids through the inlet port (1). Excess transmission charging oil either drops to the bottom of the housing to be scavenged or flows to the transmission oil cooler through the outlet hose (2). The torque converter lockup clutch solenoid (3) is energized by the Transmission/Chassis ECM when DIRECT DRIVE (lockup clutch ENGAGED) is required. Transmission charge pump supply (signal) oil flows through the small hose (4) to the lockup clutch control valve. The lockup clutch control valve then engages the lockup clutch. The transmission charging pressure relief valve is part of the transmission hydraulic control valve. The relief valve limits the maximum pressure in the transmission charging circuit. Transmission charging pressure can be measured at the tap (5).

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115

1. Transmission clutch pressure taps

Shown is the Individual Clutch Modulation (ICM) transmission hydraulic control valve. Transmission clutch pressures are measured at the pressure taps (1).

• Priority valve pressure

The transmission hydraulic control valve contains a priority valve. The priority valve controls the pressure that is directed to the selector pistons in each of the clutch stations. The transmission priority valve pressure is 1720 kPa (250 psi).

2. Transmission lube relief valve

The transmission lube pressure relief valve (2) limits the maximum pressure in the transmission lube circuit.

3. "D" Station controls dual stage relief valve

The "D" Station (3) is used to control the dual stage relief valve setting for the clutch supply pressure. In DIRECT DRIVE, the pressure measured at the tap for station "D" will be approximately 1380 kPa (200 psi). This valve station is adjusted to obtain the correct transmission charge pressure in DIRECT DRIVE. At LOW IDLE in TORQUE CONVERTER DRIVE, transmission charging pressure should be 2515 kPa (365 psi) minimum. At HIGH IDLE in TORQUE CONVERTER DRIVE, transmission charging pressure should be 3175 kPa (460 psi) maximum.

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• Test clutch pressures in DIRECT DRIVE

4. Torque converter lockup signal line - Disconnect and plug to test in DIRECT DRIVE

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During torque converter lockup (DIRECT DRIVE), clutch supply pressure is reduced to extend the life of the transmission clutch seals. At 1300 rpm in DIRECT DRIVE, the clutch supply pressure should be 2020 + 240 - 100 kPa (293 + 35 - 15 psi). The corresponding transmission charge pressure is reduced to 2100 ± 100 kPa (305 ± 15 psi). To test the transmission clutch pressures in torque converter lockup (DIRECT DRIVE), disconnect the signal line (4) and install a plug in the hose and a cap on the fitting. An 8T5200 Signal Generator/Counter can be used to shift the transmission during the diagnostic tests. If a Signal Generator is not available, disconnect the upshift and downshift solenoids and rotate the rotary selector spool manually by inserting a 1/4 in. ratchet extension through the transmission case.

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TRANSMISSION ICM HYDRAULIC SYSTEM LOCKUP SOLENOID

UPSHIFT PRESSURE

DOWNSHIFT UPSHIFT SOLENOID SOLENOID

DOWNSHIFT PRESSURE

A

ROTARY ACTUATOR

ON 3

E N1

TO TORQUE CONVERTER RELAY VALVE

NEUTRALIZER VALVE PRIORITY REDUCTION VALVE

PILOT OIL PRESSURE

B

ROTARY SELECTOR SPOOL

PUMP PRESSURE

F

FILTERS

CHARGING PUMP

LUBE PUMP

C

SCAVENGE PUMP

OIL COOLER

G D

COOLER BY VALVE

H

LUBE PRESSURE

RELIEF VALVE TRANSMISSION TANK TRANSMISSION CASE

SELECTOR VALVE GROUP

LOCKUP DUAL STAGE RELIEF VALVE

PRESSURE CONTROL GROUP

LUBRICATION RELIEF VALVE

116 • ICM transmission controls

• Dual stage relief valve

Shown is a sectional view of the ICM transmission hydraulic control valve group. The rotary selector spool is in a position that engages two clutches. Pump supply oil from the lockup solenoid flows to the selector piston in station "D." Station "D" reduces the pump supply pressure, and the reduced pressure flows to the lower end of the relief valve. Providing oil pressure to the lower end of the relief valve reduces the clutch supply pressure.

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785C/789C TRANSMISSION HYDRAULIC SYSTEM

TRANSMISSION CHARGING FILTER

TRANSMISSION LUBE FILTER TRANSMISSION OIL COOLER

SIGNAL TO LOCKUP VALVE RELAY

TRANSMISSION PUMP

LUBE PORT

MAGNETIC SCAVENGE SCREENS

117 • Transmission hydraulic system

Shown is the transmission hydraulic system. The transmission pump pulls oil through a suction screen from the transmission tank.

• Three section pump:

The three section transmission pump is mounted on the rear of the pump drive, which is located inside the right frame near the torque converter. The three sections are:

- Transmission scavenge - Transmission lube - Transmission charging

- Transmission scavenge - Transmission lube - Transmission charging The transmission scavenge section pulls oil through the magnetic screens located at the bottom of the transmission. The scavenged oil from the transmission is sent to the transmission tank.

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• Transmission charging section

Oil flows from the charging section of the transmission pump to the transmission charging filter. Oil flows from the transmission charging filter to the transmission control valve located on top of the transmission. Transmission charging oil flows from the transmission control valve and s with the oil from the transmission lube section of the transmission pump.

• Transmission lube section

Oil flows from the lube section of the transmission pump to the transmission lube filter. Oil from the transmission lube filter and the transmission control valve flows through the transmission oil cooler. Oil flows from the transmission oil cooler to the transfer gears and the transmission to cool and lubricate the internal components.

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118

Differential 1. Rear axle pump

Shown is the differential removed from the rear axle housing. The rear axle cooling and filter system starts with a rear axle pump (1) that is driven by the differential. Since the pump rotates only when the machine is moving, no oil flow is produced when the machine is stationary. Cooling oil flow increases with ground speed to provide cooling when it is most needed.

2. Rear axle suction screen

The rear axle pump pulls oil from the bottom of the rear axle housing through a suction screen (2). Oil flows from the pump through a temperature and flow control valve located on top of the differential housing to a filter mounted on the rear of the axle housing. Oil then flows from the filter back to the valve located on top of the differential housing. Oil then flows from the valve to the rear wheel bearings and the differential bearings.

3. Differential bearing oil tubes

Oil flows through tubes (3) to the differential bearings.

4. Fiberglass shroud

The fiberglass shroud (4) reduces the temperature of the rear axle oil on long hauls by reducing the oil being splashed by the bevel gear.

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1. Pump supply hose to flow control valve 2. Rear axle temperature and flow control valve 3. Differential oil temperature sensor 4. Differential oil pressure sensor

Oil flows from the pump through the large hose (1) to the rear axle temperature and flow control valve (2). A differential oil temperature sensor (3) and pressure sensor (4) are located on the temperature and flow control valve. The sensors provide input signals to the Brake ECM. The Brake ECM sends signals to the VIMS. The differential temperature sensor input signal is used to warn the operator of a high rear axle oil temperature condition or to turn on the attachment rear axle cooling fan (if equipped). The differential oil pressure sensor input signal is used to warn the operator of a HIGH or LOW rear axle oil pressure condition. A LOW oil pressure warning is provided if the pressure is below 35 kPa (5 psi) when the differential oil temperature is above 52°C (125°F) and the ground speed is higher than 24 km/h (15 mph). A HIGH oil pressure warning is provided if the pressure is above 690 kPa (100 psi) when the differential oil temperature is above 52°C (125°F).

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The temperature and pressure control valve (2) prevents high oil pressure when the rear axle oil is cold. When the oil temperature is below 43°C (110°F), the valve is OPEN and allows oil to flow to the rear axle housing. When the oil temperature is above 43°C (110°F), the valve is CLOSED and all the oil flows through the filter to a flow control valve located in the temperature and flow control valve. The temperature and pressure control valve is also the system main relief valve. If the pressure exceeds 690 kPa (100 psi), the temperature and pressure control valve will open to prevent high oil pressure to the rear axle oil filter. The flow control valve distributes the oil flow to the rear wheel bearings and the differential bearings. 5. Differential bearing oil supply hose

Oil flows from the temperature and flow control valve to the differential oil filter mounted on the rear of the axle housing. Oil then flows from the filter back to the temperature and flow control valve. Some of the oil that flows from the temperature and flow control valve flows through the small supply hose (5) to the differential bearings.

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1. Differential oil filter by switch 2. Rear axle oil level switches

The differential oil filter by switch (1) and the two rear axle oil level switches (2) (one behind differential filter) provide input signals to the Brake ECM. The Brake ECM sends signals to the VIMS. The differential oil filter by switch signal is used to warn the operator when the differential oil filter is restricted. The rear axle oil level switch input signals are used to warn the operator when the rear axle oil level is LOW.

• Differential oil filter service information

When the truck is initially put into operation, a 1R0719 (40 micron) filter is installed. This filter removes the rust inhibitor used during manufacturing. The 40 micron filter should be changed after the first 50 hours of operation and replaced with a 4T3131 (13 micron) filter. The 13 micron filter should be changed every 500 hours.

3. Differential carrier thrust pin cover

A differential carrier thrust pin is located behind the small cover (3). The thrust pin prevents movement of the differential carrier during high thrust load conditions.

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REAR AXLE OIL COOLING AND FILTER SYSTEM OIL COOLER

OIL FILTER

FLOW CONTROL VALVE TEMPERATURE/ PRESSURE CONTROL VALVE

DIFFERENTIAL OIL PUMP

REAR AXLE

SUCTION SCREEN

121 • Rear axle oil cooling and filter system

• Temperature and pressure control valve

Shown is a schematic of the rear axle oil cooling and filter system. The differential oil pump pulls oil from the bottom of the rear axle housing through a suction screen. Oil flows from the pump through a temperature and flow control valve located on top of the differential housing. The temperature and pressure control valve, which is part of the temperature and flow control valve, prevents high oil pressure when the rear axle oil is cold. When the oil temperature is below 43°C (110°F), the valve is OPEN and allows oil to flow to the rear axle housing. When the oil temperature is above 43°C (110°F), the valve is CLOSED and all the oil flows through the differential oil filter and the oil cooler (if equipped) to a flow control valve, which is also part of the temperature and flow control valve.

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• Temperature and pressure control valve is main relief

• Flow control valve prevents overfilling compartments

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The temperature and pressure control valve is also the system main relief valve. If the pressure exceeds 690 kPa (100 psi), the temperature and pressure control valve will open to prevent high oil pressure to the rear axle oil filter. The flow control valve distributes the oil flow to the rear wheel bearings and the differential bearings. At high ground speeds, excess oil flow is diverted to the axle housing to prevent overfilling the wheel bearing and final drive compartments.

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FIRST REDUCTION RING GEAR

SECOND REDUCTION RING GEAR

SECOND REDUCTION CARRIER SECOND REDUCTION PLANETARY GEAR

SECOND REDUCTION SUN GEAR

FINAL DRIVE

FIRST REDUCTION SUN GEAR

FIRST REDUCTION CARRIER FIRST REDUCTION PLANETARY GEAR

122 • Double reduction planetary gear final drives

Final Drives Shown is a sectional view of the double reduction planetary gear final drive. Power flows from the differential through axles to the sun gear of the first reduction planetary set. The ring gears of the first reduction planetary set and the second reduction planetary set cannot rotate. Since the ring gears cannot rotate, the first reduction sun gear causes rotation of the first reduction planetary gears and the first reduction carrier. The first reduction carrier is splined to the second reduction sun gear. The second reduction sun gear causes rotation of the second reduction planetary gears and the second reduction carrier. Since the second reduction carrier is connected to the wheel assembly, the wheel assembly also rotates. The wheel assembly rotates much slower than the axle shaft but with increased torque.

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123

Transmission/Chassis Electronic Control System • Transmission/Chassis ECM (arrow)

The Transmission/Chassis Electronic Control Module (ECM) (arrow) is located in the compartment at the rear of the cab. The transmission control used in the "B" Series trucks is referred to as the second generation Electronic Programmable Transmission Control (EPTC II). The transmission control used in the "C" Series trucks performs the transmission control functions, plus some other machine functions (hoist control). Because of the added functionality of the control, it is now referred to as the "Transmission/Chassis ECM."

• Transmission/Chassis ECM - No diagnostic window - Diagnostics and programming require ECAP or ET • Transmission/Chassis ECM looks like Engine ECM

The Transmission/Chassis ECM does not have a diagnostic window as in the EPTC II. Diagnostic and programming functions must be performed with an Electronic Control Analyzer Programmer (ECAP) or a laptop computer with the Electronic Technician (ET) software installed. ET is the tool of choice because the Transmission/Chassis ECM can be reprogrammed with a "flash" file using the WinFlash application of ET. The ECAP cannot "flash" files. The Transmission/Chassis ECM appears identical to the Engine ECM with two 40-pin connectors, but the Transmission/Chassis ECM does not have fittings for cooling fluid. Also, the Transmission/Chassis ECM has no access plate for a personality module.

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"C" SERIES TRUCK TRANSMISSION/CHASSIS ELECTRONIC CONTROL SYSTEM

OUTPUT COMPONENTS

INPUT COMPONENTS SHIFT LEVER POSITION SWITCH

TRANSMISSION GEAR SWITCH

CAT DATA LINK ELECTRONIC SERVICE TOOL ENGINE ECM

TRANSMISSION OUTPUT SPEED SENSOR

BRAKE ECM

CONVERTER OUTPUT SPEED SENSOR SERVICE/RETARDER BRAKE PRESSURE SWITCH

VIMS

ENGINE OUTPUT SPEED SENSOR

UPSHIFT SOLENOID PARKING/SECONDARY BRAKE PRESSURE SWITCH

BODY POSITION SENSOR

DOWNSHIFT SOLENOID KEY START SWITCH

LOCKUP SOLENOID

LOW STEERING PRESSURE SWITCH HOIST LEVER POSITION SENSOR

STARTER SOLENOID

BACK-UP ALARM RELAY

HOIST SCREEN SWITCH AUTO LUBE SOLENOID

TRANSMISSION OIL TEMP SENSOR TRANSMISSION CHARGE FILTER SWITCH

BODY UP LAMP HOIST LOWER SOLENOID

TRANSMISSION LUBE FILTER SWITCH TORQUE CONVERTER OIL TEMP SENSOR

HOIST RAISE SOLENOID

124 • ECM shifts transmission

The purpose of the Transmission/Chassis ECM is to determine the desired transmission gear and energize solenoids to shift the transmission up or down as required based on information from both the operator and machine.

• Shifts controlled by electrical signals

The Transmission/Chassis ECM receives information (electrical signals) from various input components such as the shift lever switch, Transmission Output Speed (TOS) sensor, transmission gear switch, body position sensor and the hoist lever sensor. Based on the input information, the Transmission/Chassis ECM determines whether the transmission should upshift, downshift, engage the lockup clutch or limit the transmission gear. These actions are accomplished by sending signals to various output components.

• Output components

Output components include the upshift, downshift and lockup solenoids, the back-up alarm and others.

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The Transmission/Chassis ECM also provides the service technician with enhanced diagnostic capabilities through the use of onboard memory, which stores diagnostic codes for retrieval at the time of service. • Benefits of electronic communication

The Engine Electronic Control, the Brake Electronic Control System (ARC and TCS), the Vital Information Management System (VIMS) and the Transmission/Chassis Electronic Control System all communicate through the CAT Data Link. Communication between the electronic controls allows the sensors of each system to be shared. Many additional benefits are provided, such as Controlled Throttle Shifting (CTS). CTS occurs when the Transmission/Chassis ECM signals the Engine ECM to reduce or increase engine fuel during a shift to lower stress to the power train.

• Transmission/Chassis ECM controls hoist and other systems

The Transmission/Chassis ECM is also used to control the hoist, the automatic lubrication (grease), the neutral-start and the back-up alarm systems on the "C" Series trucks.

• Sensors signal Transmission/Chassis ECM

Many of the sensors and switches that provided input signals to the VIMS interface modules on the "B" Series trucks have been moved to provide input signals to the Transmission/Chassis ECM and the Brake ECM. Sensors and switches that were in the VIMS and now provide input signals to the Transmission/Chassis ECM are: - Low steering pressure - Hoist screen by - Transmission oil temperature - Transmission charge filter by - Transmission lube filter by - Torque converter oil temperature

• Diagnostic and programming functions

The Electronic Control Analyzer Programmer (ECAP) and the Electronic Technician (ET) Service Tools can be used to perform several diagnostic and programming functions. Some of the diagnostic and programming functions that the service tools can perform are: - Display real time status of input and output parameters - Display the internal clock hour reading - Display the number of occurrences and the hour reading of the first and last occurrence for each logged diagnostic code and event - Display the definition for each logged diagnostic code and event - Display load counters - Display the lockup clutch engagement counter - Display the transmission gear shift counter - Program the top gear limit and the body up gear limit - new Flash files

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125 1. Shift lever switch - Switch-type input

The shift lever (also referred to as the "Cane" or "Gear Selector") switch (1) is located inside the cab in the shift console and provides input signals to the Transmission/Chassis ECM. The shift lever switch controls the desired top gear selected by the operator. The shift lever switch inputs consist of six wires. Five of the six wires provide codes to the Transmission/Chassis ECM. Each code is unique for each position of the shift lever switch. Each shift lever switch position results in two of the five wires sending a ground signal to the Transmission/Chassis ECM. The other three wires remain open (ungrounded). The pair of grounded wires is unique for each shift lever position. The sixth wire is the "Ground " wire, which is normally grounded. The Ground wire is used to that the shift lever switch is connected to the Transmission/Chassis ECM. The Ground wire allows the Transmission/Chassis ECM to distinguish between loss of the shift lever switch signals and a condition in which the shift lever switch is between detent positions.

• Shift lever switch diagnostics

To view the shift lever switch positions or diagnose problems with the switch, use the VIMS message center module or the status screen of the ET service tool and observe the "Gear Lever" status. As the shift lever is moved through the detent positions, the Gear Lever status should display the corresponding lever position shown on the shift console.

2. Shift lever adjustment nuts

The position of the shift lever can be changed to obtain better alignment with the gear position numbers on the shift console by loosening the three nuts (2) and rotating the lever. The position of the shift lever switch is also adjustable with the two screws (3).

3. Shift lever switch adjustment screws

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126 1. Transmission gear switch - Switch type input

The transmission gear switch (1) provides input signals to the Transmission/Chassis ECM. The transmission gear switch inputs (also referred to as the "actual gear inputs") consist of six wires. Five of the six wires provide codes to the Transmission/Chassis ECM. Each code is unique for each position of the transmission gear switch. Each transmission gear switch position results in two of the five wires sending a ground signal to the Transmission/Chassis ECM. The other three wires remain open (ungrounded). The pair of grounded wires is unique for each gear position. The sixth wire is the "Ground " wire, which is normally grounded. The Ground wire is used to that the transmission gear switch is connected to the Transmission/Chassis ECM. The Ground wire allows the Transmission/Chassis ECM to distinguish between loss of the transmission gear switch signals and a condition in which the transmission gear switch is between gear detent positions. Earlier transmission gear switches use a wiper assembly that does not require a power supply to Pin 4 of the switch. Current transmission gear switches are Hall-Effect type switches. A power supply is required to power the switch. A small magnet es over the Hall cells, which then provide a non- position switching capability. The Hall-Effect type switch uses the same 24-Volt power supply used to power the Transmission/Chassis ECM.

2. Upshift solenoid 3. Downshift solenoid 4. Lockup solenoid

The solenoid outputs provide +Battery voltage to the upshift solenoid (2), the downshift solenoid (3) or the lockup solenoid (4) based on the input information from the operator and the machine. The solenoids are energized until the transmission actual gear switch signals the Transmission/Chassis ECM that a new gear position has been reached.

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127 • TOS sensor (arrow)

The Transmission Output Speed (TOS) sensor (arrow) is located on the transfer gear housing on the input side of the transmission. Although the sensor is physically located near the input side of the transmission, the sensor is measuring the speed of the transmission output shaft. The sensor is a Hall-Effect type sensor. Therefore, a power supply is required to power the sensor. The sensor receives 10 Volts from the Transmission/Chassis ECM. The sensor output is a square wave signal of approximately 10 Volts amplitude. The frequency in Hz of the square wave is exactly equal to twice the output shaft rpm. The signal from this sensor is used for automatic shifting of the transmission. The signal is also used to drive the speedometer and as an input to other electronic controls.

• Engine rpm is calculated for shift points

The Transmission/Chassis ECM uses the TOS sensor to determine when to shift, but the shifts always occur at a precise engine rpm. The engine rpm is known because the Transmission/Chassis ECM knows the gear ratios of the transfer gear, each gear range of the transmission, the differential and the final drives. The Transmission/Chassis ECM also estimates the circumference of the tires. The Transmission/Chassis ECM uses the gear ratios and tire circumference to calculate the engine rpm for any ground speed.

• 8T5200 Signal Generator/Counter

An 8T5200 Signal Generator/Counter can be used to shift the transmission during diagnostic tests. Disconnect the harness from the lockup solenoid and the speed sensor and attach the Signal Generator to the speed sensor harness. Depress the ON and HI frequency buttons. Start the engine and move the shift lever to the highest gear position. Rotate the frequency dial to increase the ground speed and the transmission will shift.

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128 1. Service/retarder brake switch

• Service/retarder brakes engaged: - Raises shift points - Eliminates anti-hunt timer

The service/retarder brake switch (1) is located in the compartment behind the cab. The switch is normally closed and opens when service/retarder brake air pressure is applied. The switch has two functions for the Transmission/Chassis ECM: - Signals the Transmission/Chassis ECM to use elevated shift points, which provide increased engine speed during downhill retarding for increased oil flow to the brake cooling circuit. - Signals the Transmission/Chassis ECM to allow rapid shifting during braking by overriding the anti-hunt timer. A diagnostic code is stored if the Transmission/Chassis ECM does not receive a closed (ground) signal from the switch within seven hours of operation time or an open signal from the switch within two hours of operation time.

• Service/retarder switch used as TCS input

The Traction Control System (TCS) also uses the service/retarder brake switch as an input through the CAT Data Link (see Slide No. 199).

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• Parking/secondary brakes engaged: - Eliminates anti-hunt timer - Signals parked machine

3. Relays

• Hoist lever sensor - Reverse inhibitor operation

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The parking/secondary brake switch (2) is in the parking/secondary brake air pressure line. The normally open switch is closed during the application of air pressure. The purpose of the switch is to signal the Transmission/Chassis ECM when the parking/secondary brakes are ENGAGED. Since the parking/secondary brakes are spring engaged and pressure released, the parking/secondary brake switch is closed when the brakes are RELEASED and opens when the brakes are ENGAGED. This signal is used to override the anti-hunt timer for rapid downshifting and is used to sense when the machine is parked. A diagnostic code is stored if the Transmission/Chassis ECM does not receive a closed (ground) signal from the switch within seven hours of operation time or an open signal from the switch within one hour of operation time. Many relays (3) are located behind the cab. Some of these relays receive output signals from the Transmission/Chassis ECM, and the relays turn on the desired function. The back-up alarm relay is one of the Transmission/Chassis ECM output components located behind the cab. When the operator moves the shift lever to REVERSE, the Transmission/Chassis ECM provides a signal to the back-up alarm relay, which turns ON the back-up alarm. Another input to the Transmission/Chassis ECM is the hoist lever sensor (see Slide No. 157). The main function of the hoist lever sensor is to raise and lower the body, but it is also used to NEUTRALIZE the transmission. If the transmission is in REVERSE when the body is being raised, the hoist lever sensor is used to shift the transmission to NEUTRAL. The transmission will remain in NEUTRAL until: - The hoist lever is moved into the HOLD or FLOAT position. - The shift lever has been cycled into and out of NEUTRAL.

4. System air pressure sensor 5. Brake light switch

The system air pressure sensor (4) and the brake light switch (5) are also located in the compartment behind the cab. The low air pressure sensor provides an input signal to the Brake ECM. The Brake ECM sends a signal to the VIMS, which informs the operator of the system air pressure condition.

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129 1. Body position sensor 2. Body position rod assembly

• Body position sensor rod adjustment

The body position sensor (1) is located on the frame near the left body pivot pin. A rod assembly (2) is connected between the sensor and the body. When the body is raised, the rod rotates the sensor, which changes the Pulse Width Modulated (PWM) signal that is sent to the Transmission/Chassis ECM. The adjustment of the rod between the sensor and the body is very important. The length of the rod must be within 10 mm (.39 in.) of the following dimensions (center to center of the rod ends): 785C: 350 ± 3 mm (13.78 ± .12 in.) 789C: 50 ± 3 mm (13.78 ± .12 in.)

• Body position sensor calibration

After the rod has been adjusted, a calibration should be performed. The body position sensor is calibrated by the Transmission/Chassis ECM when the following conditions occur: -

Engine is running Hoist lever is in FLOAT No ground speed is present for one minute Body position is 6 degrees different than previous calibration Duty cycle output from the sensor is less than 20%

Use the VIMS display to view the body position. When the body is down, the VIMS should display zero degrees. If the position is greater than zero degrees, the sensor rod may have to be adjusted.

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The body position signal is used for several purposes. • Body up gear limit

• Hoist SNUB control

• Body up warnings

Body up gear limiting Hoist snubbing Starts a TPMS cycle Signals a new load count (after 10 seconds in RAISE position) Lights the body up dash lamp Allows the VIMS to provide body up warnings

The body position sensor signal is used to limit the top gear into which the transmission will shift when the body is UP. The body up gear limit value is programmable from FIRST to THIRD gear using the ECAP or ET service tool. The Transmission/Chassis ECM comes from the factory with this value set to FIRST gear. When driving away from a dump site, the transmission will not shift past the programmed gear until the body is down. If the transmission is already above the limit gear when the body goes up, no limiting action will take place. The body position sensor signal is also used to control the SNUB position of the hoist control valve. When the body is being lowered, the Transmission/Chassis ECM signals the hoist LOWER solenoid to move the hoist valve spool to the SNUB position. In the SNUB position, the body float speed is reduced to prevent the body from making hard with the frame. The body position sensor signal is used to provide warnings to the operator when the truck is moving with the body UP. The faster the ground speed, the more serious the warning. INSTRUCTOR NOTE: In the previous slides, only some of the input and output components of the transmission and chassis control were shown. Other components will be shown when the system they control is discussed (hoist solenoids for example).

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STEERING 789C

130

STEERING SYSTEM • Steering hydraulically operated

• Secondary steering uses accumulators

• "C" Series steering system same as "B" Series

This section of the presentation explains the operation of the steering system. As on other Caterpillar Off-highway Trucks, the steering system uses hydraulic force to change the direction of the front wheels. The system has no mechanical connection between the steering wheel and the steering cylinders. If the oil flow is interrupted while the truck is moving, the system incorporates a secondary steering system. Secondary steering is accomplished by accumulators which supply oil flow to maintain steering. The steering system on the "C" Series trucks is the same as the steering system on the "B" Series trucks. No changes were made to the steering system.

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789C STEERING SYSTEM HIGH STEERING PRESSURE SWITCH

NO STEER/MAXIMUM FLOW STEERING DIRECTIONAL VALVE

SOLENOID AND RELIEF VALVE RETURN MANIFOLD

R

L

P

CASE DRAIN FILTER

T LS

PISTON PUMP

LOW STEERING PRESSURE SWITCH

ACCUMULATOR CHARGING VALVE HAND METERING UNIT

131 • 789C steering system

When the engine is started, oil for the steering system is drawn from the steering hydraulic tank by the steering pump and sent through a one-way check valve to the solenoid and relief valve manifold. Oil from the solenoid and relief valve manifold flows to the steering directional valve, the accumulator charging valve and the accumulators. After the oil pressure increases to a predetermined pressure in both accumulators, the steering pump will destroke.

• Accumulators supply oil for normal and secondary steering

When a steering demand occurs, the accumulators supply the necessary oil flow for steering, and pressure in the accumulators decreases. When the oil pressure in the accumulators decreases to a predetermined level, the steering pump will automatically upstroke to maintain the oil pressure required for steering in the accumulators.

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• Accumulators direct oil to steering directional valve

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Oil from the accumulators flows through the steering directional valve to the Hand Metering Unit (HMU). If the steering wheel is not turned, the oil flows through the HMU and the main steering oil filter to the tank.

• Orifice in HMU provides "thermal bleed" to prevent seizure

• Steering directional valve directs oil to steering cylinders

Allowing oil to circulate through the HMU while the steering wheel is stationary provides a "thermal bleed" condition, which maintains a temperature differential of less than 28°C (50°F) between the HMU and the tank. This "thermal bleed" prevents thermal seizure of the HMU (sticking steering wheel). When the steering wheel is turned, the HMU directs oil back to the steering directional valve. The steering directional valve directs oil to the steering cylinders. Depending on which direction the steering wheel is turned, oil will flow to the head end of one steering cylinder and to the rod end of the other cylinder. The action of the oil on the pistons and rods in the steering cylinders causes the wheels to change direction. Displaced oil from the steering cylinders flows through the back pressure valve in the steering directional valve and returns through the main steering oil filter to the tank.

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785C STEERING SYSTEM HOLD

CASE DRAIN FILTER CROSSOVER RELIEF VALVES

PISTON PUMP PUMP SWITCH

HAND METERING UNIT

SOLENOID AND RELIEF VALVE RETURN MANIFOLD

132 • 785C steering system

Oil from the steering pump flows through a one-way check valve to the solenoid and relief valve return manifold and is then sent to the accumulators and the Hand Metering Unit (HMU). The 785C truck does not use a steering directional valve. Oil from the HMU flows through a crossover relief valve group directly to the steering cylinders.

• Orifice in HMU provides "thermal bleed" to prevent seizure

In the HOLD position, oil flows through an orifice in the HMU to the tank. Allowing oil to flow through the HMU in the HOLD position provides a "thermal bleed" condition, which prevents thermal seizure of the HMU (sticking steering wheel).

• Crossover relief valves protect cylinders and lines

The crossover relief valves protect the steering cylinders and oil lines from pressure surges when the steering wheel is in the HOLD position by equalizing the oil pressure between the head ends and rod ends of the steering cylinders.

• HMU directs oil to crossover relief valves and steer cylinders

During a turn, the HMU directs oil through the crossover relief valves to the steering cylinders. Displaced oil from the steering cylinders flows back through the HMU to the main steering oil filter.

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3

5

4

1

2 6

133

• Steering tank 1. Upper sight gauge 2. Lower sight gauge

The steering tank is located on the right platform. Two sight gauges are on the side of the tank. When the engine is shut off and the oil is cold, the oil should be visible between the FULL and ADD OIL markings of the upper sight gauge (l). When the engine is running and the accumulators are fully charged, the oil level should not be below the ENGINE RUNNING marking of the lower sight gauge (2). If the ENGINE RUNNING level is not correct, check the nitrogen charge in each accumulator. A low nitrogen charge will allow excess oil to be stored in the accumulators and will reduce the secondary steering capacity.

3. Pressure release button

A combination vacuum breaker/pressure relief valve is used to limit the tank pressure. Before removing the fill cap, be sure that the engine was shut off with the key start switch and the oil has returned to the tank from the accumulators. Depress the pressure release button (3) on the breather to vent any remaining pressure from the tank.

4. Case drain filter

Supply oil for the steering system is provided by a piston-type pump. Case drain oil from the pump returns to the tank through the filter (4). The remaining steering system oil returns to the tank through the main steering filter (5). Both filters are equipped with by valves to protect the system if the filters are restricted or during cold oil start-up.

5. Main steering filter

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6. APU secondary steering connector

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If the steering pump fails or if the engine cannot be started, the connector (6) is used to attach an Auxiliary Power Unit (APU). The APU will provide supply oil from the steering tank at the connector to charge the steering accumulators. Steering capability is then available to tow the truck. INSTRUCTOR NOTE: For more information on using the APU, refer to the Special Instructions "Using 1U5000 Auxiliary Power Unit (APU)" (Form SEHS8715) and "Using the 1U5525 Attachment Group" (Form SEHS8880).

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2 1

134

1. 785C steering pump

The piston-type steering pump (1) for the 785C truck is mounted to the pump drive. The pump drive is located on the inside of the right frame rail near the torque converter. The steering pump operates only when the engine is running and provides the necessary oil flow to the accumulators for steering system operation.

2. Pressure compensator valve

The steering pump for the 785C truck contains a pressure compensator valve (2) that monitors and controls steering pump output.

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785C STEERING PUMP MAXIMUM FLOW SWASHPLATE

PISTON SUPPLY OIL

OUTPUT OIL

SPRING

CONTROL PISTON

PRESSURE COMPENSATOR VALVE

135 • 785C steering pump - Maximum flow • Swashplate at maximum angle allows maximum flow

Shown is a sectional view of the piston-type steering pump for the 785C truck in the MAXIMUM FLOW condition. No oil pressure is present in the control piston. In this condition, the swashplate is kept at maximum angle by the force of the spring in the pump housing. The pistons travel in and out of the barrel and maximum flow is provided through the outlet port. Since the pump is driven by a shaft off the engine, it should be ed that engine rpm also affects pump output.

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PUMP COMPENSATOR VALVE MAXIMUM PUMP FLOW

DRAIN AGES

MINIMUM PUMP FLOW

FROM PUMP

DRAIN AGES

TO CONTROL PISTON

FROM PUMP TO CONTROL PISTON

136 • 785C pump compensator valve - Maximum flow

- Minimum flow/maximum pressure

• Adjust compensator with shims

Shown is a sectional view of the pump compensator valve for the 785C truck. The pump compensator valve senses pump supply pressure through a age in the valve body. When the outlet pressure is less than the force of the spring on the end of the compensator spool, the oil is blocked from flowing to the pump control piston. As the accumulators fill, the pressure of the oil through the pump outlet increases. The pump supply pressure will increase until the pressure of the oil in the pump age in the pump compensator valve is high enough to overcome the spring force on the compensator spool. The spool then moves to the left and opens the age to the control piston. This movement occurs when the outlet oil pressure is approximately 17580 ± 345 kPa (2550 ± 50 psi). The pressure setting can be adjusted by changing the shim thickness behind the compensator spool spring. Remove the plug and add shims to increase the pressure setting. Remove shims to lower the setting.

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785C STEERING PUMP MINIIMUM FLOW SWASHPLATE

PISTON SUPPLY OIL

OUTPUT OIL

CONTROL PISTON

PRESSURE COMPENSATOR VALVE

137 • 785C steering pump - Minimum flow/maximum pressure

The pressure of the oil from the compensator valve age moves the control piston, which rotates the swashplate toward the minimum angle. The pistons now have very little movement in and out of the barrel as the retraction plate and slippers follow the minimum angle of the swashplate. While the accumulators are filled, this small movement of the pistons maintains the pressure at the setting of the pressure compensator valve. The compensator spool will remain open to provide pressure oil behind the control piston. Excess oil from the pump outlet goes into the pump case for cooling and lubrication. The oil then goes through a drain line to the case drain oil filter and steering hydraulic tank.

• Pump returns to maximum flow

As the steering wheel is turned and oil is taken from the accumulators, the pressure at the pump outlet will decrease. When accumulator pressure decreases, the pressure compensator valve will allow the swashplate to move toward maximum angle and increase pump output.

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3

4

1

2

138 1. Steering pump

The 789C is equipped with a load sensing, pressure compensated, piston-type pump (1). The steering pump is mounted to the pump drive. The pump drive is located on the inside of the right frame rail near the torque converter.

2. Load sensing controller

The steering pump operates only when the engine is running and provides the necessary flow of oil to the accumulators for steering system operation. The steering pump contains a load sensing controller (2) that works with an accumulator charging valve to monitor and control steering pump output.

• CUT-OUT pressure

The steering pump will produce flow at high pressure until the steering accumulators are charged with oil and the pressure increases to 18300 ± 350 kPa (2655 ± 50 psi) at LOW IDLE. This pressure is referred to as the CUT-OUT pressure. When the CUT-OUT pressure is reached, the accumulator charging valve reduces the load sensing signal pressure to the pump load sensing controller, and the pump destrokes to the LOW PRESSURE STANDBY condition. During LOW PRESSURE STANDBY, the pressure should be between 2070 and 3600 kPa (300 and 525 psi).

• LOW PRESSURE STANDBY

• CUT-IN pressure

The pump operates at minimum swashplate angle to supply oil for lubrication and leakage. Because of the normal leakage in the steering system and Hand Metering Unit (HMU) "thermal bleed", the pressure in the accumulators will gradually decrease to 16470 ± 350 kPa (2390 ± 50 psi). This pressure is referred to as the CUT-IN pressure.

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When the pressure in the accumulators decreases to the CUT-IN pressure, the accumulator charging valve blocks the load sensing signal line to the load sensing controller from returning to the tank, and the pump upstrokes to maximum displacement (full flow). 3. LOW PRESSURE STANDBY pressure tap

A pressure tap (3) is located on the pump pressure switch manifold. If steering pump supply pressure is measured at this tap during LOW PRESSURE STANDBY, a gauge acceptable for testing maximum steering system pressure must be used to avoid damaging the gauge when the steering pump upstrokes to provide maximum oil flow.

4. Low steering pressure switch

Two pressure switches monitor the condition of the steering system on the 789C. One switch (4) monitors the output of the steering pump. This switch monitors pump supply pressure during LOW PRESSURE STANDBY. The VIMS refers to this switch as the "low steering pressure" switch.

• High steering pressure switch

The other steering pressure switch is mounted on the bottom of one of the steering accumulators (see Slide No. 153). This switch monitors the steering system accumulator pressure. The VIMS refers to this switch as the "high steering pressure" switch.

• Steering pressure warning only above 8 km/h (5 mph)

Both steering pressure switches provide input signals to the Transmission/Chassis ECM. The Transmission/Chassis ECM sends signals to the VIMS, which informs the operator of the condition of the steering system. A steering system warning is only displayed if the ground speed is above 8 km/h (5 mph) or the actual gear switch is not in NEUTRAL.

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1 2

4

3

6

5

139

• 789C trucks 1. Check valve 2. Solenoid and relief valve manifold 3. Accumulator charging valve 4. Steering directional valve 5. Steering system pressure tap 6. Steering system S•O•S tap

On the 789C truck, steering pump supply oil flows through a check valve (1) to the solenoid and relief valve manifold (2). The solenoid and relief valve manifold connects the steering pump to the accumulator charging valve (3), the accumulators and the steering directional valve (4). The solenoid and relief valve manifold also provides a path to drain for the steering oil. When checking the steering system CUT-OUT and CUT-IN pressures, a gauge can be connected at the pressure tap (5). Steering system oil samples can be taken at the steering system Scheduled Oil Sampling (S•O•S) tap (6).

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789C STEERING PUMP MAXIMUM FLOW FROM ACCUMULATORS

TO ACCUMULATORS ACCUMULATOR CHARGING VALVE

PUMP OUTPUT ACTUATOR PISTON

LOAD SENSING PRESSURE

FLOW COMPENSATOR

LOAD SENSING CONTROLLER SWASHPLATE PISTON

140 • Steering pump operation • Actuator piston drained during maximum flow

After the engine is started, pressure increases in the steering accumulators. The pump load sensing controller is spring biased to vent the actuator piston pressure to drain. Venting pressure from the load sensing controller and the actuator piston positions the spring biased swashplate to maximum displacement (full flow). As pressure increases in the accumulators, pump supply pressure is sensed in the accumulator charging valve and on both ends of the flow compensator. With pressure on both ends of the flow compensator, the swashplate is kept at maximum angle by the force of the spring in the pump housing and pump discharge pressure on the swashplate piston. The pistons travel in and out of the barrel and maximum flow is provided through the outlet port. Since the pump is driven by the engine, engine rpm also affects pump output. NOTE: Because the signal lines are sensing pump supply pressure and not a "load" pressure, the steering system does not operate the same as other load sensing systems with a margin pressure.

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789C STEERING PUMP LOW PRESSURE STANDBY FROM ACCUMULATORS

TO ACCUMULATORS ACCUMULATOR CHARGING VALVE

PUMP OUTPUT

ACTUATOR PISTON

LOAD SENSING PRESSURE

FLOW COMPENSATOR LOAD SENSING CONTROLLER SWASHPLATE PISTON

141 • Accumulator charging valve shifts • Signal pressure decreases

• Pump at LOW PRESSURE STANDBY

Pump supply pressure will increase until the accumulator pressure acting on the accumulator charging valve shifts the spool, and the load sensing signal pressure is vented to the tank. The accumulator charging valve spool shifts (cut-out) when the pump outlet oil pressure is approximately 18300 ± 350 kPa (2655 ± 50 psi). An orifice prevents supply pressure from filling the drained load sensing age above the flow compensator. Pump oil (at low pressure standby pressure) flows past the lower end of the displaced flow compensator spool to the actuator piston. The actuator piston has a larger surface area than the swashplate piston. The oil pressure at the actuator piston overcomes the spring force of the swashplate piston and moves the swashplate to destroke the pump. The pump is then at a low flow, LOW PRESSURE STANDBY condition. Pump output pressure is equal to the setting of the flow compensator. The LOW PRESSURE STANDBY setting must be between 2070 and 3600 kPa (300 and 525 psi).

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In the NEUTRAL or NO STEER position, demand for oil from the accumulators is low. The pump operates at minimum swashplate angle to supply oil for lubrication and leakage. Because of the normal leakage in the steering system and HMU "thermal bleed.", the pressure in the accumulators will gradually decrease to approximately 16470 ± 350 kPa (2390 ± 50 psi) (90% of the accumulator charging valve cut-out pressure). • Charging valve shifts when accumulator pressure decreases • Pump returns to full flow

• Steering pump cycle time

When the pressure in the accumulators decreases to 16470 ± 350 kPa (2390 ± 50 psi), the accumulator charging valve shifts (cut-in) and blocks the load sensing signal line pressure from the tank. Pump supply oil flows through the orifice and pressurizes the load sensing signal line. The load sensing signal shifts the flow compensator spool and drains the actuator piston oil to the tank. Venting pressure from the actuator piston positions the spring biased swashplate to maximum displacement (full flow). At LOW lDLE in the NEUTRAL or NO STEER position, the pump will cycle between the cut-out and cut-in conditions in 25 seconds or more. Connecting a pressure gauge to the pressure tap on the bottom of the steering directional valve will indicate these steering system pressures. If pump pressure cycles in less than 25 seconds, leakage is in the system and must be corrected. Typical sources of leakage can be the accumulator bleed down solenoid or the back-up relief valve located on the return manifold.

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2

1

3

142 1. Accumulator charging valve

Shown is the accumulator charging valve (1). The accumulator charging valve is located on the frame rail near the front of the truck and below the engine oil pan.

• Adjusting charging valve

The pressure setting of the accumulator charging valve can be changed by adjusting the spring force that keeps the valve seated (closed). Change the setting by removing the protective cap (2) and turning the adjustment screw clockwise to increase or counterclockwise to decrease the pressure setting. Do not exceed 14 N•m (10 lb. ft.) torque on the adjustment screw when making the adjustments. One turn of the adjustment screw changes the pressure approximately 4000 kPa (580 psi).

2. Protective cap

Operate the engine at LOW IDLE and check the pump (accumulator) pressure at the pressure tap (3). The pump will cycle between cut-out and cut-in every 25 seconds or more. The pressure gauge will indicate these steering system pressures. Turn the adjusting screw until the cut-out pressure is correct. If the accumulator charging pressure cannot be adjusted within specifications, an adjustment of the high pressure cutoff valve is required. The high pressure cutoff setting must be a minimum of 1720 kPa (250 psi) higher than the accumulator charging valve setting. • Allow three charging cycles before testing pressures

NOTE: When testing or adjusting any steering system pressure settings, always allow the accumulator charge cycle to occur at least three times before testing the pressures. Failure to allow the charging cycle to occur three times will result in inaccurate readings.

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LOAD SENSING CONTROLLER

FROM ACCUMULATOR ACCUMULATOR CHARGING VALVE TO ACCUMULATOR DISCONNECT AND PLUG LINE FOR HIGH PRESSURE CUTOFF TEST

HIGH PRESSURE CUTOFF ADJUSTMENT SCREW

LOW PRESSURE STANDBY ADJUSTMENT SCREW

TO TANK TO ACTUATOR PISTON FROM PUMP OUTPUT PORT

143 • Adjusting high pressure cutoff - Disconnect load sensing line

- Adjust high pressure cutoff adjusting screw

• Cutoff setting must be higher than charging valve setting

Pump pressure limiting (high pressure cutoff) is adjustable. To adjust the pump high pressure cutoff valve, turn the accumulator charging valve adjustment screw all the way in, or disconnect the load sensing (LS) line (pump to accumulator charging valve) at the pump. Plug the line to the accumulator charging valve and cap the fitting on the pump. Operate the engine at LOW IDLE, and check the pump (accumulator) pressure at the pressure tap below the steering directional valve. Turn the compensator (high pressure cutoff) adjusting screw while watching the pressure gauge. One turn is equal to approximately 2800 kPa (405 psi). Adjust the pressure to 20000 ± 350 kPa (2900 ± 50 psi). When the adjustment is complete, reconnect the LS line to the pump. The high pressure cutoff setting must be a minimum of 1720 kPa (250 psi) higher than the accumulator charging valve setting. If the high pressure cutoff setting of the compensator valve (in the load sensing controller) is lower than the accumulator charging valve setting, the pump will stay at MINIMUM FLOW, and the steering system will take too long to recharge. The high pressure cutoff adjustment provides a back-up if the accumulator charging valve malfunctions.

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• Adjusting low pressure standby

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Pump LOW PRESSURE STANDBY is also adjustable. Connect a gauge to the low pressure standby pressure tap (see Slide No. 138). With the signal line connected, operate the engine at LOW IDLE and check the pump pressure. The pump will cycle to low pressure standby every 25 seconds or more. Low pressure standby must be between 2070 and 3600 kPa (300 and 525 psi). If adjustment is required, stop the engine. Turn the low pressure standby adjustment screw clockwise to increase the pressure and counterclockwise to decrease the pressure until the pressure is between 2070 and 3600 kPa (300 and 525 psi). Each 1/4 turn changes the pressure setting approximately 345 kPa (50 psi). NOTE: If the steering pump is adjusted on a hydraulic test stand, set the margin pressure to 2070 ± 100 kPa (300 ± 15 psi) with a flow of 115 ± 12 L/min (30 ± 3 gpm), 1838 rpm and 15000 kPa (2180 psi) discharge pressure. The low pressure standby reading measured on a truck is higher than the test stand margin pressure due to parasitic loads in the truck steering system.

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1 5

2 4 3

144

• 789C solenoid and relief valve manifold

On the 789C truck, steering pump supply oil flows through a check valve (1) to the solenoid and relief valve manifold. The solenoid and relief valve manifold connects the steering pump to the accumulator charging valve, the accumulators and the steering directional valve. The solenoid and relief valve manifold also provides a path to drain for the steering oil.

1. Check valve

The check valve (1) prevents accumulator oil from flowing back to the steering pump when the pump destrokes to LOW PRESSURE STANDBY.

2. Accumulator bleed down solenoid

The accumulator bleed down solenoid (2) drains pressure oil from the accumulators when the truck is not in operation.

3. Back-up relief valve

The back-up relief valve (3) protects the system from pressure spikes if the pump cannot destroke fast enough or limits the maximum pressure if the steering pump high pressure cutoff valve does not open.

4. Steering system S•O•S tap

Steering system oil samples can be taken at the steering system Scheduled Oil Sampling (S•O•S) tap (4)

5. Secondary steering connector

To operate the steering system on a disabled truck, an Auxiliary Power Unit (APU) can be connected to the secondary steering connector (5) on the solenoid and relief valve manifold and to a suction port on the hydraulic tank (see Slide No. 133). The APU will provide supply oil to charge the accumulators. Steering capability is then available to tow the truck.

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5 6

1

4 2

3

145

• 785C solenoid and relief valve manifold

1. Check valve

• Accumulator bleed down solenoid (not shown) 2. Back-up relief valve

On the 785C truck, steering pump supply oil flows through a check valve (1) to the solenoid and relief valve manifold. The solenoid and relief valve manifold connects the steering pump to the accumulators and the HMU. The solenoid and relief valve manifold also provides a path to drain for the steering oil. The check valve (1) prevents accumulator oil from flowing back to the steering pump The accumulator bleed down solenoid (not shown) drains pressure oil from the accumulators when the truck is not in operation. The back-up relief valve (2) limits the maximum pressure if the steering pump compensator valve fails. Steering system oil samples can be taken at the steering system Scheduled Oil Sampling (S•O•S) tap (3)

3. Steering system S•O•S tap 4. Secondary steering connector

5. Steering accumulator 6. Steering system pressure tap

To operate the steering system on a disabled truck, an Auxiliary Power Unit (APU) can be connected to the secondary steering connector (4) on the solenoid and relief valve manifold and to a suction port on the hydraulic tank (see Slide No. 133). The APU will provide supply oil to charge the accumulators. Steering capability is then available to tow the truck. The 785C has two accumulators (5). The steering system pressure tap (6) is located on the bottom of the left steering accumulator.

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SOLENOID AND RELIEF VALVE MANIFOLD FROM ACCUMULATORS

TO TANK

BLEED DOWN SOLENOID BACKUP RELIEF VALVE

146 • Solenoid and relief valve manifold

Shown is a sectional view of the solenoid and relief valve manifold. The accumulator bleed down solenoid is energized by the bleed down solenoid shutdown control (see Slide No. 154) when the key start switch is moved to the OFF position. The bleed down solenoid shutdown control holds the solenoid open for 70 seconds.

• Bleed down solenoid drains accumulators

Pressure oil from the accumulators is sensed by the bleed down solenoid. When the solenoid is ENERGIZED, the plunger moves and connects the pressure oil to the drain age. Pressure oil flows through an orifice, past the plunger, to the tank. The orifice limits the return oil flow from the accumulators to a rate which is lower than the flow limit (restriction) of the steering oil filter in the hydraulic tank. When the solenoid is DE-ENERGIZED, spring force moves the plunger and pressure oil cannot go to drain.

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• Back-up relief valve protects system if pump does not destroke

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The back-up relief valve protects the steering system if the steering pump malfunctions (fails to destroke). Pressure oil from the steering pump works against the end of the back-up relief valve and the spring. The relief valve unseats (opens) if the pressure reaches approximately: 785C: 22740 ± 350 kPa (3300 ± 50 psi) at 8 ± 2 L/min (2 ± .5 gpm) 789C: 20670 ± 400 kPa (3000 ± 60 psi) at 8 ± 2 L/min (2 ± .5 gpm) Oil then flows past the relief valve and drains to the tank.

• Adjust back-up relief valve on test bench only

• Functional test of back-up relief valve (on machine)

The back-up relief valve must be adjusted only on a test bench. The pressure setting of the back-up relief valve can be changed by adjusting the spring force that keeps the relief valve seated (closed). To change the relief valve setting, remove the protective cap and turn the adjustment screw clockwise to increase or counterclockwise to decrease the pressure setting. One revolution of the setscrew will change the pressure setting 3800 kPa (550 psi). A functional test of the back-up relief valve can be performed on the machine by installing a manual hydraulic pump at the location of the Auxiliary Power Unit (APU) connector and installing blocker plates to prevent oil from flowing to the accumulators. See the service manual for more detailed information. NOTE: Using the functional test procedure to adjust the back-up relief valve will provide only an approximate setting. Accurate setting of the back-up relief valve can only be performed on a hydraulic test bench.

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1

2

147

1. 789C steering directional valve

The steering directional valve (1) used on the 789C truck is pilot operated from the HMU in the operator’s station. Five pilot lines connect these two components. The pilot lines send pilot oil from the HMU to shift the spools in the steering directional valve. The spools control the amount and direction of pressure oil sent to the steering cylinders. Four pilot lines are used for pump supply, tank return, left turn and right turn. The fifth pilot line is for the load sensing signal.

2. Steering system pressure tap

When checking the steering system cut-out and cut-in pressures, a gauge can be connected at the pressure tap (2).

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LEFT TURN CYLINDER

TO TANK

RIGHT TURN CYLINDER

RELIEF/MAKEUP VALVE

BACK PRESSURE VALVE RELIEF/MAKEUP VALVE

STEERING DIRECTIONAL VALVE NO TURN

RIGHT TURN PILOT OIL

LEFT TURN PILOT OIL

COMBINER/CHECK SPOOL

AMPLIFIER SPOOL

PRIORITY SPOOL LOAD SENSING PORT FROM ACCUMULATOR

HAND METERING UNIT SUPPLY AND THERMAL BLEED

148 • Steering directional valve components: - Priority spool - Amplifier spool with combiner/check spool - Directional spool - Relief/makeup valves - Back pressure valve

Shown is a sectional view of the steering directional valve. The main components of the steering directional valve are: the priority spool, the amplifier spool with internal combiner/check spool, the directional spool, the relief/makeup valves and the back pressure valve. Pressure oil from the accumulators flows past the spring biased priority spool and is blocked by the amplifier spool. The same pressure oil flows through an orifice to the right end of the priority spool. The orifice stabilizes the flow to the priority spool and must be present to open and close the priority spool as the flow demand changes. The same pressure oil flows to the HMU. After all the ages fill with pressure oil, the priority spool shifts to the left, but remains partially open. In this position, the priority spool allows a small amount of oil flow (thermal bleed) to the HMU and decreases the pressure to the HMU supply port. The "thermal bleed" prevents the HMU from sticking.

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• Steering directional valve in NO STEER position

With the truck in the NEUTRAL or NO TURN position, all four working ports (supply, tank, right turn and left turn) are vented to the tank through the HMU. The directional spool is held in the center position by the centering springs.

• Relief/makeup valves

While the truck is traveling straight (no steer), any rolling resistance (opposition) acting on the steering cylinders creates a pressure increase. The increased pressure acts on the relief/makeup valve in that port. If the pressure increase exceeds 28000 ± 1000 kPa (4065 ± 150 psi), the relief poppet will open. A pressure drop occurs across the orifice. The pressure drop causes the dump valve to move and allows oil to flow to the tank age.

• External impact opens a relief valve and a makeup valve

The relief action causes the makeup portion of the other relief/makeup valve to open and replenish oil to the low pressure ends of the cylinders. • Back pressure valve sends pressure to makeup valve

The excess (dumped) oil flows across the back pressure valve and enters the outer end of the other relief/makeup valve. A pressure difference of 48 kPa (7 psi) between the tank age and the low pressure cylinder port causes the makeup valve to open. The excess oil flows into the low pressure cylinder port to prevent cavitation of the cylinder. The back pressure valve also prevents cavitation of the cylinders by providing a positive pressure of 170 kPa (25 psi) in the age behind the makeup valve. A pressure higher than 170 kPa (25 psi) will open the back pressure valve to the tank.

• Adjust relief/makeup valves on test bench only • Functional test of relief/makeup valves (on machine)

The steering directional valve must be removed and tested on a hydraulic test bench to accurately check the setting of the relief/makeup valves. A functional test of the relief/makeup valves can be performed on the machine by connecting a manual hydraulic pump and installing blocker plates to prevent oil from flowing to the steering cylinders. See the service manual for more detailed information. NOTE: Using the functional test procedure to adjust the relief/makeup valves will provide only an approximate setting. Accurate setting of the relief/makeup valves can only be performed on a hydraulic test bench.

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LEFT TURN CYLINDER

TO TANK

RIGHT TURN CYLINDER

BACK PRESSURE VALVE

RELIEF/MAKEUP VALVE RELIEF/MAKEUP VALVE

STEERING DIRECTIONAL VALVE RIGHT TURN RIGHT TURN PILOT OIL

LEFT TURN PILOT OIL AMPLIFIER SPOOL

COMBINER/CHECK SPOOL

PRIORITY SPOOL LOAD SENSING PORT FROM ACCUMULATOR

HAND METERING UNIT SUPPLY AND THERMAL BLEED

149 • Steering directional valve during a RIGHT TURN

• Load sensing pilot pressure moves priority spool

• Pilot oil moves directional spool

When the steering wheel is turned to the RIGHT, the "thermal bleed" and venting of the four work ports to the tank is stopped. The increased supply pressure flows to the HMU and the load sensing pilot line. The load sensing pilot line directs cylinder pressure to the priority spool in the directional valve. Cylinder pressure is present in the HMU because pilot oil combines with accumulator oil in the combiner/check valve spool in the directional valve. The increased pressure in the load sensing line causes the priority spool to move to the right and allows more oil flow to the HMU through the supply line. The load sensing port supply pressure varies with the steering load. The priority spool moves proportionally, allowing sufficient oil flow to meet the steering requirements. Pilot oil flows through a stabilizing orifice to the right turn pilot port of the directional valve and moves the directional spool. Movement of the directional spool allows pilot oil to flow to the amplifier and combiner/check spools.

STMG 706 11/98

• Pilot oil moves amplifier spool

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The pilot oil divides at the amplifier spool. Pilot oil flows through a narrow groove around the combiner/check spool. The pilot oil is momentarily blocked until the amplifier spool moves far enough to the right to allow partial oil flow through one of eight orifices. Pilot oil also flows through a connecting pin hole and a stabilizing orifice to the left end of the amplifier spool and causes the amplifier spool to move to the right. Accumulator oil at the spring end (right end) of the amplifier spool flows through a mid-connecting pin to the left end of the amplifier spool and also causes the amplifier spool to move to the right.

• Pilot and accumulator oil combine in combiner/check spool

When the amplifier spool moves to the right, accumulator oil flows to the inner chamber, forcing the combiner/check spool to the left. Accumulator oil then flows through seven of the eight orifices. Pilot and accumulator oil combine. Oil flows across the directional spool (which has already shifted) for a RIGHT TURN.

• Turning steering wheel faster provides more flow to cylinders

The faster the steering wheel is turned, the farther the directional spool and the amplifier spool are shifted. A higher flow rate is available, which causes the truck to turn faster. The ratio of pilot and pump supply oil that combine is always the same because one orifice is dedicated to pilot flow and seven orifices are dedicated to accumulator supply flow. Return oil from the cylinders flows across the directional spool, around the relief/makeup valve, forces the back pressure valve open and returns to the tank.

• Pressure spike moves combiner/check spool and blocks flow to HMU

During a turn, if a front wheel strikes a large obstruction that cannot move, oil pressure in that steering cylinder and oil line increases. Oil flow to the cylinder is reversed. This pressure spike is felt in the amplifier spool. The combiner/check spool moves to the right and blocks the seven pump supply oil orifices to the steering cylinders. The amplifier spool moves to the left and blocks the pilot oil orifice. Pilot oil flow to the steering cylinders stops. The pressure spike is not felt at the HMU. If the pressure spike is large enough, the relief/makeup valve drains the pressure oil to the tank as previously described.

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4 2

3 1

150 1. 785C solenoid and relief valve manifold

Shown is the solenoid and relief valve manifold (1) and the crossover relief valves (2) on the 785C truck.

2. Crossover relief valves

The crossover relief valves (2) are located in one housing mounted on the inside of the left frame rail near the front of the truck. The crossover relief valves prevent damage from high pressure oil in the steering cylinder circuit caused by an outside force applied to a front wheel when the steering wheel is stationary.

- Protect cylinders and lines 3. Pressure taps

• Pressure difference could indicate incorrect crossover relief valve setting

4. Steering system pressure switch

The crossover relief valve housing contains two pressure taps (3) where steering system pressure can be measured. One tap shows pressure during a left turn and the other tap shows pressure during a right turn. To check the steering system pressure, turn the steering wheel completely in either direction. Operate the engine at LOW IDLE. Continue to turn the steering wheel after the wheels have stopped and the pressure will increase to the pump compensator valve setting. Check the steering pressure while turning in both directions. The pump compensator valve setting should be observed on the gauge in both directions. If the pressure readings are different, one of the crossover relief valve settings is probably incorrect. A misadjusted valve must be removed and readjusted on a test bench. On the 785C, one pressure switch (4) monitors the condition of the steering system. The switch provides an input signal to the Transmission/Chassis ECM. The Transmission/Chassis ECM sends a signal to the VIMS.

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785C CROSSOVER RELIEF SYSTEM EXTERNAL IMPACT

CROSSOVER RELIEF VALVES

HAND METERING UNIT

151 • Crossover relief valves equalize pressure between steering cylinders

On the 785C truck, when the steering wheel is stationary, the HMU blocks oil in the steering cylinders and in the lines between the steering cylinders and the HMU. The oil blockage prevents the front wheels from moving when the steering wheel is not turned. If pressure is applied against the front wheels while the steering wheel is stationary, the pressure of the oil increases in the head end of one cylinder and the rod end of the other cylinder. If the increase of oil pressure exceeds 18270 kPa (2650 psi) at the affected crossover relief valve, the valve will open. Oil from the high pressure ends of the steering cylinders then transfers to the low pressure ends of the cylinders.

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152

• 789C HMU (arrow)

The 789C Hand Metering Unit (HMU) (arrow) is located at the base of the steering column behind a cover at the front of the cab. The HMU is connected to the steering wheel and controlled by the operator.

• 789C meters oil to directional valve

The 789C HMU meters the amount of oil sent to the steering directional valve by the speed at which the steering wheel is turned. The faster the HMU is turned, the higher the flow sent to the steering cylinders from the steering directional valve, and the faster the wheels will change direction.

• 785C HMU is larger to handle more flow

The 785C HMU is larger because oil flows directly from the HMU, through the crossover relief valve, to the steering cylinders. The capacity of the 785C HMU must be large enough to handle the flow required to fill the steering cylinders and allow satisfactory steering cycle times.

• HMU ports

On the front of the HMU are four ports: - Return to tank

- Left turn

- Pump supply

- Right turn

The 789C HMU has a fifth port on the side of the HMU. The fifth port is the load sensing signal line to the steering directional valve.

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1

2

153 1. 789C steering accumulators

Two steering accumulators (1) provide the supply oil during normal operation and temporary secondary steering if a loss of pump flow occurs (789C shown). Inside each accumulator is a rubber bladder that is charged with nitrogen. The nitrogen charge provides energy for normal steering and secondary steering capability if steering pump flow stops.

• Check secondary steering

To check the secondary steering system, the engine must be shut off with the manual shutdown switch (see Slide No. 25) while leaving the key start switch in the ON position. When the manual shutdown switch is used, the bleed down solenoid is not energized and the accumulators do not bleed down. The truck can then be steered with the engine stopped.

2. Steering accumulator pressure switch

The steering accumulator pressure switch (2) monitors the steering accumulator pressure. The switch provides an input to the VIMS. The VIMS refers to this switch as the "high steering pressure" switch. WARNING High pressure oil remains in the accumulators if the manual shutdown switch is used. To release the oil pressure in the accumulators, turn the key start switch to the OFF position and turn the steering wheel left and right until the oil is drained from the accumulators (steering wheel can no longer be turned).

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154

• Shutdown control (arrow)

Shown is the shutdown control (arrow) for the steering accumulator bleed down solenoid. The control is located in the compartment behind the cab. The steering accumulator bleed down solenoid is activated by the control when the key start switch is moved to the OFF position. The bleed down solenoid shutdown control holds the solenoid open for 70 seconds. The charge pressure for the steering accumulators is:

• Accumulator charge pressures

785C: 8270 ± 0 kPa (1200 ± 0 psi) 789C: 5512 ± 345 kPa (800 ± 50 psi)

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HOIST SYSTEM 789C

155 HOIST SYSTEM • Hoist system controlled by Transmission/Chassis ECM

The hoist system on the 785C and 789C trucks is electronically controlled by the Transmission/Chassis ECM. The hoist control system operates similarly to the earlier trucks. The four operating positions are: RAISE, HOLD, FLOAT and LOWER.

• Hoist SNUB control

The hoist valve has a fifth position referred to as the SNUB position. The operator is unaware of the SNUB position because a corresponding lever position is not provided. When the body is being lowered, just before the body s the frame, the Transmission/Chassis ECM signals the hoist solenoids to move the hoist valve spool to the SNUB position. In the SNUB position, the body float speed is reduced to prevent the body from making hard with the frame.

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156

• Hoist lever (arrow)

The operator controls the hoist lever (arrow). The four positions of the hoist lever are RAISE, HOLD, FLOAT and LOWER.

• Hoist lever normally in FLOAT position

The truck should normally be operated with the hoist lever in the FLOAT position. Traveling with the hoist in the FLOAT position will make sure the weight of the body is on the frame and body pads and not on the hoist cylinders. The hoist control valve will actually be in the SNUB position. NOTE: If the truck is started with the body raised and the hoist lever in FLOAT, the lever must be moved into HOLD and then FLOAT before the body will lower.

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157

• Hoist control position sensor (arrow) • Sensor energizes two solenoids on hoist valve

• Hoist lever sensor provides modulation • Hoist lever sensor performs two functions:

The hoist lever controls a Pulse Width Modulated (PWM) position sensor (arrow). The PWM sensor sends duty cycle input signals to the Transmission/Chassis ECM. Depending on the position of the sensor and the corresponding duty cycle, one of the two solenoids located on the hoist valve is energized. The four positions of the hoist lever are RAISE, HOLD, FLOAT and LOWER but since the sensor provides a duty cycle signal that changes for all positions of the hoist lever, the operator can modulate the speed of the hoist cylinders. The hoist lever sensor also replaces the body raise switch (transmission neutralizer switch) that was located behind the operator’s seat. The hoist lever sensor performs two functions:

- Raises and lowers body

- Raises and lowers the body

- Neutralizes transmission in REVERSE

- Neutralizes the transmission in REVERSE

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3

1

2

158

1. Hoist, converter and brake tank 2. Oil level sight gauges

- Lower gauge for filling tank with cylinders RAISED

• Use only TDTO oil

Shown is the hoist, converter and brake oil hydraulic tank (1) and the oil level sight gauges (2). The oil level is normally checked with the upper sight gauge. The oil level should first be checked with cold oil and the engine stopped. The level should again be checked with warm oil and the engine running. The lower sight gauge is used when filling the hydraulic tank with the hoist cylinders in the RAISED position. When the hoist cylinders are lowered, the hydraulic oil level will increase. After the hoist cylinders are lowered, check the hydraulic tank oil level with the upper sight gauge as explained above. Use only Transmission Drive Train Oil (TDTO) with a specification of TO-4 or newer. TDTO-4 oil: - Provides maximum frictional capability required for clutch discs used in the brakes. - Increases brake holding capability by reducing brake slippage. - Controls brake chatter.

3. Breather

Check the hydraulic tank breather (3) for restriction. Clean the filter if it is restricted.

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159

• Rear of tanks • Hoist suction screens (arrows)

Shown is the rear of the transmission and hoist, converter and brake oil hydraulic tanks. The hoist system pumps pull oil from the hydraulic tank through the suction screens (arrows) located in the rear of the tank.

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2 2

1

160

1. Two section hoist pump 2. Hoist system pressure taps

The hoist system oil for the "C" Series Trucks is supplied by a two section pump (1) located at the top rear of the pump drive. Oil flows from the hoist pump through two screens to the hoist valve. The hoist system pressure can be tested at the two pressure taps (2). The hoist system relief pressures are different in the RAISE and LOWER positions.

• Hoist pressures during RAISE

The hoist system relief pressure during RAISE is: 17225 + 700 - 0 kPa (2500 + 100 - 0 psi)

• Hoist pressures during LOWER

The hoist system relief pressure during LOWER is: 3450 + 350 - 0 kPa (500 + 50 - 0 psi)

• Body position sensor must be in RAISE to test LOWER pressure • Hoist pressures during HOLD, FLOAT and SNUB

When the body is in the DOWN position, the hoist valve will be in the SNUB position. The body position sensor rod must be disconnected from the body and the sensor must be rotated to the RAISE position before the LOWER relief pressure can be tested. In the HOLD, FLOAT and SNUB positions, the gauge will show the brake cooling system pressure, which is a result of the restriction in the coolers, brakes and hoses (normally much lower than the actual oil cooler relief valve setting). The maximum pressure is limited by the oil cooler relief valve, which has a setting of 790 ± 20 kPa (115 ± 3 psi).

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2

1

161

1. Hoist screens 2. Hoist screen by switches

Oil flows from the hoist pump through the hoist screens (1) to the hoist control valve. Two hoist screen by switches (2) provide input signals to the Transmission/Chassis ECM. The Transmission/Chassis ECM sends signals to the VIMS, which informs the operator if the hoist screens are restricted.

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4

3

2

1

5

7 6

162

1. Pump supply ports

2. Load check valve plugs

3. RAISE relief valve 4. LOWER relief valve

Oil flows from the hoist pump through two ports (1) (only one visible in this view) to the hoist control valve located inside the right frame next to the hoist cylinder. Two load check valves, one for each pump port, are located below the two plugs (2). The load check valves remain closed until the pump supply pressure is higher than the pressure in the hoist cylinders. The load check valves prevent the body from dropping before the RAISE pressure increases. The hoist system relief pressures are different in the RAISE and LOWER positions. The RAISE relief valve (3) controls the pressure in the hoist system during RAISE. The LOWER relief valve (4) controls the pressure in the hoist system during LOWER. The relief valve housing must be removed to install shims (see Slide No. 164).

6. Oil cooler port

Oil flows through the drain port (5) to the hydraulic tank. When the hoist valve is in the HOLD, FLOAT or SNUB position, all the hoist pump oil flows through two ports (6), one on each side of the hoist valve, to the two rear brake oil coolers located on the right side of the engine.

7. Brake oil cooling pressure port

Brake cooling oil pressure can be checked at the test port (7) by removing the plug and installing a pressure tap.

5. Tank return port

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4

6 5

7 2

1

3

163

1. Counterbalance valve

2. Counterbalance valve signal pressure port

3. Rear brake oil cooler relief valve

A counterbalance valve (1) is mounted on the left side of the hoist valve. The counterbalance valve prevents cavitation of the cylinders when the body raises faster than the pumps can supply oil to the cylinders (caused by a sudden shift of the load). The counterbalance valve signal pressure can be checked at the test port (2) by removing the plug and installing a pressure tap. The counterbalance signal pressure is equal to the RAISE pressure. An oil cooler relief valve is located behind the large plug (3). The oil cooler relief valve limits the rear brake oil cooling pressure when the hoist valve is in the HOLD, FLOAT or SNUB position. The setting of the oil cooler relief valve is 790 kPa (115 psi).

• Hoist pilot oil supplied by parking brake system

The hoist valve uses parking brake release pressure as the pilot oil to shift the directional spool inside the hoist valve. The parking brake release pressure is 4700 ± 200 kPa (680 ± 30 psi).

4. RAISE position solenoid valve

Pilot pressure is always present at both ends of the directional spool. Two solenoid valves are used to drain the pilot oil from the ends of the directional spool, which then allows the spool to move. On the left is the RAISE solenoid valve (4), and on the right is the LOWER solenoid valve (5).

5. LOWER position solenoid valve

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• Hoist solenoids "dither" in HOLD

The RAISE and LOWER solenoid valves are always receiving approximately 300 millivolts at a frequency of 80 Hz when they are in any position except HOLD. The excitation, referred to as "dither," is used to keep the solenoids in a ready state for quick response.

• Hoist solenoids receive between 0 and 1.9 amps

When the Transmission/Chassis ECM receives an input signal from the hoist lever sensor, the Transmission/Chassis ECM sends an output signal current between 0 and 1.9 amps to one of the solenoids. The amount of current sent to the solenoid determines the amount of pilot oil that is drained from the end of the directional spool and, therefore, the distance that the directional spool travels toward the solenoid.

6. RAISE port

Oil flows through two upper ports (6), one on each side of the hoist valve, to RAISE the hoist cylinders. Oil flows through two lower ports (7), one on each side of the hoist valve, to LOWER the hoist cylinders.

7. LOWER port

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LOWER SOLENOID

PARKING BRAKE RELEASE PRESSURE

"C" SERIES HOIST CONTROL VALVE HOLD

REAR BRAKE OIL COOLER RELIEF VALVE

TO TANK

TO HOIST CYLINDER HEAD END

LOAD CHECK VALVE

TO HOIST CYLINDER ROD END LOW PRESSURE RELIEF VALVE COUNTERBALANCE VALVE

HIGH PRESSURE RELIEF VALVE

ROD END VENT SLOT

DUAL STAGE RELIEF VALVE SIGNAL STEM

TO REAR BRAKE OIL COOLERS

PUMP SUPPLY PORT

PARKING BRAKE RELEASE PRESSURE

RAISE SOLENOID

164 • Hoist valve in HOLD

• Hoist supply oil flows to rear brake cooling

Shown is a sectional view of the hoist valve in the HOLD position. Pilot oil pressure is directed to both ends of the directional spool. The spool is held in the centered position by the centering springs and the pilot oil. ages in the directional spool vent the dual stage relief valve signal stem to the tank. All the hoist pump oil flows through the rear brake oil coolers to the rear brakes. The position of the directional spool blocks the oil in the head end of the hoist cylinders. Oil in the rod end of the hoist cylinders is connected to the rear brake cooling oil by a small vent slot cut in the directional spool.

• Test brake cooling pressure at pumps in HOLD

A gauge connected to the hoist system pressure taps while the hoist valve is in the HOLD position will show the brake cooling system pressure, which is a result of the restriction in the coolers, brakes and hoses (normally much lower than the actual oil cooler relief valve setting). The maximum pressure in the circuit should correspond to the setting of the front brake oil cooler relief valve. The setting of the oil cooler relief valve is 790 kPa (115 psi).

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LOWER SOLENOID

"C" SERIES HOIST CONTROL VALVE

PARKING BRAKE RELEASE PRESSURE

RAISE

REAR BRAKE OIL COOLER RELIEF VALVE

TO TANK

TO HOIST CYLINDER HEAD END

LOAD CHECK VALVE

FROM HOIST CYLINDER ROD END

LOW PRESSURE RELIEF VALVE COUNTERBALANCE VALVE

HIGH PRESSURE RELIEF VALVE

ROD END VENT SLOT

DUAL STAGE RELIEF VALVE SIGNAL STEM

TO REAR BRAKE OIL COOLERS

PUMP SUPPLY PORT

PARKING BRAKE RELEASE PRESSURE

RAISE SOLENOID

165 • Hoist valve in RAISE

Shown is a sectional view of the hoist valve in the RAISE position. The RAISE solenoid is energized and drains pilot oil pressure from the lower end of the directional spool. The directional spool moves down. Pump oil flows past the directional spool to the head end of the hoist cylinders.

• Load check valve

When the directional spool is initially shifted, the two load check valves (one shown) remain closed until the pump supply pressure is higher than the pressure in the hoist cylinders. The load check valves prevent the body from dropping before the RAISE pressure increases.

• Dual stage relief signal stem

The directional spool also sends hoist cylinder raise pressure to the dual stage relief valve signal stem and the counterbalance valve. The dual stage relief valve signal stem moves down and blocks the supply pressure from opening the low pressure relief valve.

STMG 706 11/98 • Counterbalance valve

• High pressure relief setting checked during RAISE at HIGH IDLE

- 200 -

The counterbalance valve is held open by the hoist cylinder raise pressure. Oil from the rod end of the hoist cylinders flows freely to the rear brake oil coolers. If the body raises faster than the pump can supply oil to the hoist cylinders (caused by a sudden shift of the load) and the raise pressure drops below 2275 kPa (330 psi), the counterbalance valve starts to close and restricts the flow of oil from the rod end of the hoist cylinders. Restricting the flow of oil from the rod end of the hoist cylinders will slow down the cylinders and prevent cavitation. Cavitation in the hoist cylinders can cause the body to drop suddenly when the hoist lever is moved from the RAISE position to the LOWER position. The pressure in the head end of the hoist cylinders cannot exceed: 17225 + 700 - 0 kPa (2500 + 100 - 0 psi) The high pressure relief valve will open if the pressure increases above this specification. When the high pressure relief valve opens, the dump spool moves to the left, and pump oil is directed to the rear brake oil coolers. The high pressure hoist relief valve setting is checked at the two pressure taps located on the hoist pump. Check the relief pressures with the hoist lever in the RAISE position and the engine at HIGH IDLE.

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HOIST COUNTERBALANCE VALVE

HEAD END SIGNAL PRESSURE FROM PUMP

TO TANK

FROM HOIST CYLINDER ROD END

ROD END PRESSURE PISTON

TO HOIST CYLINDER ROD END

CHECK VALVE

LOWER AND FLOAT

RAISE

166 • Counterbalance valve • Head end signal pressure holds valve open

During RAISE, the counterbalance valve prevents the dump body from running ahead of the hoist pumps if the load shifts rapidly to the rear of the body and attempts to pull the hoist cylinders. Signal pressure from the head end of the hoist cylinders holds the counterbalance valve open. Oil from the rod end of the hoist cylinders flows unrestricted through the counterbalance valve to the tank. If the head end pressure decreases below 2270 kPa (330 psi), the counterbalance valve moves down and restricts the flow of oil from the rod end of the cylinders to the tank.

• Rod end pressure can open valve

If no head end signal pressure is present, rod end pressure can still open the counterbalance valve. If the rod end pressure exceeds 6900 ± 690 kPa (1000 ± 100 psi) at the rod end pressure piston, the valve will move up and allow rod end oil to flow from the cylinders to the tank.

• No restriction in LOWER and FLOAT

During LOWER and FLOAT, the counterbalance valve allows unrestricted flow from the pump through a check valve to the rod end of the hoist cylinders.

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LOWER SOLENOID

PARKING BRAKE RELEASE PRESSURE

"C" SERIES HOIST CONTROL VALVE LOWER (POWER DOWN)

REAR BRAKE OIL COOLER RELIEF VALVE

TO TANK

FROM HOIST CYLINDER HEAD END

LOAD CHECK VALVE

TO HOIST CYLINDER ROD END

LOW PRESSURE RELIEF VALVE COUNTERBALANCE VALVE

HIGH PRESSURE RELIEF VALVE

ROD END VENT SLOT

DUAL STAGE RELIEF VALVE SIGNAL STEM

TO REAR BRAKE OIL COOLERS

PUMP SUPPLY PORT

PARKING BRAKE RELEASE PRESSURE

RAISE SOLENOID

167 • Hoist valve in LOWER (power down)

Shown is a sectional view of the hoist valve in the LOWER (power down) position. The LOWER solenoid is energized and drains pilot oil pressure from the upper end of the directional spool. The directional spool moves up. Supply oil from the pump flows past the directional spool, through the counterbalance valve, to the rod end of the hoist cylinders. Oil in the head end of the hoist cylinders flows to the tank. The supply oil in the rod end of the cylinders and the weight of the body move the cylinders to their retracted positions.

• Body position sensor controls SNUB position

Just before the body s the frame, the body position sensor sends a signal to the Transmission/Chassis ECM to move the valve spool to the SNUB position. In the SNUB position, the valve spool moves slightly to restrict the flow of oil and lower the body gently.

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• Dual stage relief signal stem

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The directional spool also vents the age to the dual stage relief valve signal stem. The dual stage relief valve signal stem allows supply pressure to be limited by the low pressure relief valve. If the pressure in the rod end of the hoist cylinders exceeds 3450 + 350 - 0 kPa (500 + 50 - 0 psi), the low pressure relief valve will open. When the low pressure relief valve opens, the dump spool moves to the left and pump oil flows to the rear brake oil coolers.

• Test low pressure relief setting during LOWER at HIGH IDLE

The low pressure hoist relief valve setting is checked at the two pressure taps located on the hoist pump. Check the relief pressures with the hoist lever in the LOWER position and the engine at HIGH IDLE.

• Body position sensor must be in RAISE to test LOWER pressure

When the body is in the DOWN position, the hoist valve will be in the SNUB position. The body position sensor rod must be disconnected from the body, and the sensor must be rotated to the RAISE position before the LOWER relief pressure can be tested.

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LOWER SOLENOID

PARKING BRAKE RELEASE PRESSURE

"C" SERIES HOIST CONTROL VALVE FLOAT

REAR BRAKE OIL COOLER RELIEF VALVE

TO TANK

FROM HOIST CYLINDER HEAD END

LOAD CHECK VALVE

TO HOIST CYLINDER ROD END LOW PRESSURE RELIEF VALVE COUNTERBALANCE VALVE

HIGH PRESSURE RELIEF VALVE

ROD END VENT SLOT TO REAR BRAKE OIL COOLERS DUAL STAGE RELIEF VALVE SIGNAL STEM

PUMP SUPPLY PORT

PARKING BRAKE RELEASE PRESSURE

RAISE SOLENOID

168 • Hoist valve in FLOAT

Shown is a sectional view of the hoist valve in the FLOAT position. The LOWER solenoid is partially energized and drains part of the pilot oil pressure above the directional spool to the tank. The directional spool moves up. Because the pilot pressure is only partially drained, the directional spool does not move as far up as during LOWER. Pump supply oil flows past the directional spool, through the counterbalance valve, to the rod end of the hoist cylinders. Oil in the head end of the hoist cylinders flows to the tank. The directional valve is in a position that permits the pressure of the oil flowing to the rear brake oil coolers to be felt at the rod end of the hoist cylinders.

• Operate truck with hoist lever in FLOAT

• Valve moves to SNUB position

The truck should normally be operated with the hoist lever in the FLOAT position. Traveling with the hoist in the FLOAT position will make sure the weight of the body is on the frame and body pads and not the hoist cylinders. The hoist valve will actually be in the SNUB position. Just before the body s the frame, the body position sensor sends a signal to the Transmission/Chassis ECM to move the valve spool to the SNUB position. In the SNUB position, the valve spool moves slightly to restrict the flow of oil and lower the body gently.

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169

• Two-stage hoist cylinders

Shown are the twin two-stage hoist cylinders used to raise and lower the body.

• Body pads (arrow)

Check the condition of the body pads (arrow) for wear or damage.

• Body lower with dead engine

To LOWER the body with a dead engine, hoist pilot pressure is required. The towing pump can be used to provide the hoist pilot oil. To lower the body with a dead engine: - Turn ON the key start switch so the towing motor and the hoist solenoids can be energized. - Move the hoist lever to the RAISE position for 15 seconds, then to the FLOAT position. - Depress the brake retraction switch on the dash (see Slide No. 48).

• Body raise with dead engine

To RAISE the body with a dead engine, connect an Auxiliary Power Unit (APU) to the hoist cylinders. Follow the same procedure used to lower the body with a dead engine, except keep the hoist lever in RAISE after the 15 seconds interval. NOTE: For more information on using the APU, refer to the Special Instructions "Using 1U5000 Auxiliary Power Unit (APU)" (Form SEHS8715) and "Using the 1U5525 Attachment Group" (Form SEHS8880).

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HOIST PUMP SUCTION SCREENS

HOIST SCREENS

FROM PARKING BRAKE RELEASE VALVE PILOT OIL

HOIST SYSTEM HOLD

REAR BRAKES

TO HOIST CYLINDER ROD END

TO HOIST CYLINDER HEAD END

REAR BRAKE OIL COOLERS

170 • Hoist system

The hoist system pumps pull oil from the hydraulic tank through suction screens. Oil flows from the hoist pump through the hoist screens to the hoist control valve. The hoist valve uses parking brake release pressure as pilot oil to shift the directional spool inside the hoist valve. Two solenoid valves are used to drain the pilot oil from the ends of the directional spool. The solenoid valve on the left is energized in the RAISE position. The solenoid valve on the right is energized in the LOWER or FLOAT position. When the hoist valve is in the HOLD or FLOAT position, all the hoist pump oil flows through the rear brake oil coolers to the rear brakes.

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An oil cooler relief valve is located in the hoist valve. The relief valve limits the rear brake oil cooling pressure when the hoist valve is in the HOLD or FLOAT position. Two hydraulic cylinders are used to raise the body away from the frame of the truck. When the hoist lever is held in the RAISE position, supply oil flows to the head end of the hoist cylinders and moves the two stage cylinders to their extended lengths. The oil from the rod end of the cylinders flows through the hoist valve to the rear brake oil cooling circuit. When the hoist lever is moved to the LOWER or FLOAT position and the cylinders are extended, supply oil enters the rod end of the hoist cylinders and lowers the second stage of the cylinders. The oil from the head end of the cylinders flows through the hoist valve to the hydraulic tank.

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AIR SYSTEM AND BRAKES 789C

171 AIR SYSTEM AND BRAKES • Two brake systems: - Parking/secondary brake system - Service/retarder brake system

Two separate brake systems are used on the "C" Series trucks. The two brake systems are: the parking/secondary brake system and the service/retarder brake system. The parking/secondary brakes are spring engaged and hydraulically released. The service/retarder brakes are engaged hydraulically by an air-over-oil brake system. The "C" Series trucks are also equipped with an air system. An engine driven air compressor supplies the air and fills two tanks. Air from the tanks provides energy to perform several functions:

• Air system functions

-

Engine start-up Service and retarder brake control Secondary and parking brake control Automatic lubrication injection (grease) Horn, air seat and cab clean-out

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172

• Oil cooled brake assembly • Seals prevent oil leaks or transfer

Shown is a cutaway illustration of an oil cooled brake assembly. The brakes are environmentally sealed and adjustment free. Oil continually flows through the brake discs for cooling. Duo-Cone seals prevent the cooling oil from leaking to the ground or transferring into the axle housing. The wheel bearing adjustment must be maintained to keep the Duo-Cone seals from leaking.

• Small piston ENGAGES secondary and parking brakes

The smaller piston (yellow) is used to ENGAGE the secondary and parking brakes. The parking brakes are spring ENGAGED and hydraulically RELEASED.

• Large piston ENGAGES retarder/service brakes

The larger piston (purple) is used to ENGAGE the retarder/service brakes. The retarder/service brakes are engaged hydraulically by an air-over-oil brake system.

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173

Air Charging System • 789C air compressor

The air system is charged by an air compressor mounted on the left front of the engine. Shown is the 789C four-cylinder air compressor. The 785C has a two-cylinder air compressor.

• Air compressor governor (arrow)

System pressure is controlled by the governor (arrow). The governor maintains the system pressure between 660 and 830 kPa (95 and 120 psi).

• Air compressor governor adjustment

The governor setting can be adjusted with a screw below the cover on top of the governor. Turn the adjustment screw OUT to increase the pressure and IN to decrease the pressure.

• 789C has increased air charging capacity

The capacity of the air charging system on the 789C truck has been increased. The 789C air compressor has been increased from a twocylinder compressor to a four-cylinder compressor. To handle the increased air flow, two larger air dryers are used, and the hoses and tubing have also been increased in size.

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174

1. 789C air dryers • 785C has one air dryer

On the 789C truck, air flows from the air compressor to two air dryers (1) located behind the left front tire. The 785C has one air dryer located in front of the left front suspension cylinder.

2. Remote air supply connector

The air system can be charged from a remote air supply through a ground level connector (2) inside the left frame.

• Check desiccant

The air dryers remove contaminants and moisture from the air system. The condition of the desiccant in the air dryers should be checked every 250 hours and changed periodically (determined by the humidity of the local climate).

• Purge valve

When the air compressor governor senses that system air pressure is at the cut-out pressure of 830 kPa (120 psi), the governor sends an air pressure signal to the purge valve in the bottom of the dryers. The purge valve opens and air pressure that is trapped in the air dryers is exhausted through the desiccant, an oil filter and the purge valve.

• Air system relief valve

An air system relief valve is located on the air dryers to protect the system if the air compressor governor malfunctions.

• Heating element

A heating element in the bottom of the dryers prevents moisture in the dryers from freezing in cold weather.

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175

1. Service/retarder brake tank

Air flows through the air dryers and fills two tanks. The service/retarder brake tank (1) is located on the right platform. This tank also supplies air for the air start system. The second tank is located behind the cab and supplies air for the parking/secondary brake system.

2. Condensation drain valve

Condensation should be drained from the tank daily through the drain valve (2).

• Relief valve (not shown)

A relief valve located near the tank drain is installed in the service/retarder brake tank. This relief valve protects the air system when the air dryers have exhausted and the ball check valves in the air dryer outlet ports close. The check valves separate the air system from the air dryer relief valves.

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176

1. Pressure protection valve

Located behind the operator’s station is a pressure protection valve (1). Supply air flows from the large service/retarder brake tank, through the pressure protection valve, to the secondary air system and accessories. The pressure protection valve opens at 550 kPa (80 psi) and closes at 482 kPa (70 psi). If the secondary air lines or an accessory circuit fails, the pressure protection valve maintains a minimum of 482 kPa (70 psi) in the service/retarder brake circuit.

• Pressure protection valve test

To test the pressure protection valve, drain the air pressure to approximately 345 kPa (50 psi). Use the VIMS display to observe the brake air pressure. With the engine running at LOW IDLE, press the horn button. Record the air pressure when the horn sounds. This pressure reading is the open setting of the pressure protection valve. Slowly drain the air pressure and record the air pressure when the horn turns off. This pressure reading is the setting of the pressure protection valve when it closes.

2. Air system pressure sensor

The air system pressure sensor (2) provides an input signal to the Brake ECM. The Brake ECM sends a signal to the VIMS, which informs the operator if a problem exists in the air system.

• Other air switches behind cab

Also located behind the operator’s station are the service/retarder brake switch, the parking/secondary brake switch and the brake light switch (see Slide No. 128).

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177

• Automatic lubrication solenoid air valve (arrow)

The solenoid air valve (arrow) provides a controlled air supply for the automatic lubrication (grease) system. The solenoid air valve is controlled by the VIMS. The VIMS ENERGIZES the solenoid ten minutes after the machine is started. The VIMS keeps the solenoid ENERGIZED for 75 seconds and then DE-ENERGIZES it. Every 60 minutes thereafter, the VIMS ENERGIZES the solenoid for 75 seconds until the machine is stopped (turned off). These settings are adjustable through the VIMS keypad in the cab.

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178

• Parking/secondary brake tank

Located behind the operator’s station is the parking/secondary brake air tank. A drain valve is located on the right side of the cab. Moisture should be drained from the tank daily through the drain valve (see Slide No. 33).

• Check valve (arrow)

A check valve (arrow) prevents a loss of air if an air line breaks upstream of the air tank.

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789C AIR CHARGING SYSTEM AIR COMPRESSOR AND GOVERNOR AIR DRYERS TO AIR START SOLENOID

REMOTE SUPPLY SERVICE/RETARDER BRAKE TANK LOW AIR SENSOR

TO AUTO LUBE SOLENOID TO HORN / SEAT / CLEAN-OUT PRESSURE PROTECTION VALVE PARKING/SECONDARY BRAKE TANK

179 • 789C air charging system

This schematic shows the flow of air through the 789C air charging system. Air flows from the air compressor, through the two air dryers, to the service/retarder brake tank.

• 785C has one air dryer

The 785C air charging system is the same as the 789C, but has only one air dryer. Air from the service/retarder brake tank enters the pressure protection valve. When the pressure in the service/retarder tank reaches 550 kPa (80 psi), the pressure protection valve allows air to flow to the parking/secondary brake tank, the air start system, the automatic lubrication system and the accessory circuits (horn, air seat and cab clean-out). All tanks have a check valve at the air supply port to prevent a loss of air if a leak upstream of the tank occurs.

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180

Brake Systems • Manual retarder valve (arrow) - Engages all four service brakes - Modulates brakes better than pedal

The manual retarder valve (arrow) is controlled by the retarder lever in the cab. Normally, the retarder valve blocks air flow to the service brake relay valve near the brake master cylinders and to the front brake oil cooler diverter valve. When the retarder lever is pulled down, air flows to the service brake relay valve and the front brake oil cooler diverter valve [maximum pressure is 550 kPa (80 psi)]. The retarder lever is used to modulate the service brake engagement by metering the amount of air flow to the service brake relay valve. The retarder engages the same brakes as the service brake pedal (see Slide No. 43), but is easier to control for brake modulation.

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4 2

5

3

1

8

7

6

181

1. Service brake valve 2. Automatic Retarder Control (ARC) valve 3. Air supply manifold

The service brake valve (1) is controlled by the brake pedal in the cab. Supply air for the service brake valve, the manual retarder valve and the Automatic Retarder Control (ARC) valve (2) is supplied from the manifold (3). When the service brakes are engaged, air flows from the service brake valve to the service brake relay valve near the brake master cylinders and to the front brake oil cooler diverter valve [maximum pressure is 825 kPa (120 psi)]. The service brake valve engages the same brakes as the retarder, but does not control brake modulation as precisely as the retarder.

4. Double check valve to brake relay 5. Double check valve to front cooler diverter valve • System with highest pressure engages brakes 6. Double check valve 7. Retarder switch

Air from the service brake valve and the manual retarder valve flows through the double check valve (4) to the service brake relay valve and through the double check valve (5) to the front brake oil cooler diverter valve. If the manual retarder and the service brakes are engaged at the same time, air from the system with the highest pressure will flow through the double check valves to the service brake relay valve and to the front brake oil cooler diverter valve. Air from the manual retarder valve also flows through the double check valve (6) to the retarder switch (7). The retarder switch turns on the amber retarder lamp on the dash in the operator’s station when the manual retarder is ENGAGED (see Slide No. 47).

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The function of the Automatic Retarder Control (ARC) system is to modulate truck braking (retarding) when descending a long grade to maintain a constant engine speed. • ARC engages separate relay valve

When the ARC is engaged, air flows from the ARC valve to a separate ARC relay valve located near the brake master cylinders. Air also flows from the ARC valve through the double check valve (6) to the retarder switch (7) and through double check valve (5) to the front brake oil cooler diverter valve.

• Brakes, retarder and ARC activate brake switches

The brake light switch and the service/retarder brake switch (see Slide No. 128) are located in the supply line to the front brake oil cooler diverter valve (see Slide No. 102). The service brake valve, the manual retarder valve and the Automatic Retarder Control (ARC) valve send air to these switches when engaged.

8. Secondary brake valve

The secondary brake valve (8) is controlled by the red pedal in the cab (see Slide No. 43). When the secondary brakes are engaged, air flows from the secondary brake valve to the signal port of an inverter valve (see next slide). The inverter valve then blocks the flow of air from the secondary brake tank to the brake release valve (see Slide No. 183).

- Modulates parking brake engagement

Blocking the air from the brake release valve positions the spool in the brake release valve to drain the oil from the parking brakes, which allows the springs in the parking brake to ENGAGE the brakes. The secondary brake valve can be used to modulate parking brake engagement by metering the amount of air flow to the brake release valve. • Parking brake valve does not modulate engagement

The parking brake air valve (see Slide No. 44) on the shift console in the cab also controls the flow of air to the brake release valve, but the parking brake air valve does not modulate the parking brake application.

• Secondary and parking brake valves activate brake switch

The parking/secondary brake switch (see Slide No. 128) is located in the supply line to the brake release valve. The secondary brake valve and the parking brake air valve send air to this switch when engaged. INSTRUCTOR NOTE: The ARC system will be discussed in more detail later in this presentation.

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182

1. Inverter valve signal port 2. Inverter valve

When the secondary brakes are engaged, air flows from the secondary brake valve to the signal port (1) of the inverter valve (2). The inverter valve then blocks the flow of air from the secondary brake tank to the brake release valve. Blocking the air from the brake release valve positions the spool in the brake release valve to drain the oil from the parking brakes, which allows the springs in the parking brake to ENGAGE the brakes.

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1

5 4 3

183

1. Brake release valve

2. Brake release valve air supply hose

3. Brake release relief valve

Oil from the parking brake release pump (see Slide No. 98) flows through the parking brake release filter (see Slide No. 101) to the brake release valve (1) located inside the left frame near the torque converter. Oil flows from the parking brake release valve to the parking brake piston in the brakes when the parking brakes are released. Supply air from the parking brake air valve in the cab or the secondary brake valve flows through the small hose (2) to an air chamber in the brake release valve. The brake release valve contains an air piston that moves a spool. The spool either directs oil to RELEASE the parking brakes or drains oil to ENGAGE the parking brakes. A relief valve (3) in the brake release valve limits the system pressure for releasing the brakes. The setting of the relief valve is 4700 ± 200 kPa (680 ± 30 psi).

4. Brake makeup tank supply oil screen

Supply oil flows from the brake release valve through an orifice and a screen (4) to the brake oil makeup tank.

5. Towing pump

To release the parking brakes for service work or towing, the electric motor that turns the towing pump (5) can be energized by the brake release switch located in the cab (see Slide No. 48). The pump sends oil to the brake release valve to RELEASE the parking brakes. Towing pump pressure is controlled by a relief valve in the towing pump.

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TOWING SYSTEM

PARKING BRAKE RELEASE PUMP

PARKING BRAKE RELEASE FILTER

TO TC LOCKUP VALVE

FROM CAB SECONDARY OR PARKING BRAKE VALVE

RELIEF VALVE TO HOIST PILOT SYSTEM

PARKING BRAKE RELEASE VALVE

CHECK VALVE

TOWING PUMP AND MOTOR

TOWING PUMP RELIEF VALVE

184 • Normal parking and secondary brake operation

• Parking brake relief valve limits TC lockup and hoist pilot pressure • Parking brake release system during towing

Normally, supply oil flows from the parking brake release pump, through the parking brake release filter, to the parking brake release valve. If air pressure is present from the parking brake air valve or the secondary brake valve, supply oil flows past the relief valve, the check valve and the spool to RELEASE the parking brakes. The relief valve limits the system pressure for releasing the brakes, torque converter lockup and for the pilot oil to shift the hoist valve. The setting of the relief valve in the parking brake valve is 4700 ± 200 kPa (680 ± 30 psi). This schematic shows the flow of oil through the parking brake release system when the towing system is activated. Oil flow from the parking brake release pump has stopped. The towing motor is energized, and air pressure is present above the parking brake release valve piston. The air pressure moves the spool in the parking brake release valve down to block the drain port.

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Oil flows from the towing pump to the parking brake release valve and the parking brakes. The check valve to the right of the parking brake release filter blocks the oil from the towing pump from flowing to the parking brake release pump. • Relief valve in towing pump limits brake release pressure

During towing, the parking brake release pressure is limited by a relief valve in the towing pump. When the relief valve opens, oil transfers from the pressure side to the suction side of the towing pump. The setting of the relief valve is approximately 4480 kPa (650 psi).

• Towing pump check valve

A check valve in the outlet port of the towing pump prevents oil from flowing to the towing pump during normal operation.

• Procedure to check towing system

• Parking brake release pressures

To check the brake release system used for towing, connect a gauge to the parking brake release pressure tap on the rear axle (see Slide No. 189). Use a long gauge hose so the gauge can be held in the cab. With the parking brake air valve in the RELEASE position and the key start switch in the ON position, energize the parking brake release switch used for towing (on the dash). The parking brake release pressure should increase to 4480 kPa (650 psi). Turn off the switch when the pressure stops increasing. The parking brake release pressure must increase to a minimum of 3790 kPa (550 psi). The parking brakes start to release between 3100 and 3445 kPa (450 and 500 psi). During towing, the brake release switch on the dash must be energized whenever the parking brake release pressure decreases below this level or the brakes will drag. The parking brakes are fully released between 3445 and 3860 kPa (500 and 560 psi).

NOTE: A minimum of 550 kPa (80 psi) air pressure must be available at the parking brake release valve to ensure full release of the brakes for towing.

NOTICE Activate the brake release switch only when additional pressure is required to release the brakes. Leaving the brake release (towing) motor energized continuously will drain the batteries. The parking brake release pressure setting must not exceed 5445 kPa (790 psi). Exceeding this pressure can cause internal damage to the brake assembly.

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PARKING/SECONDARY BRAKES SECONDARY BRAKES RELEASED PARKING BRAKES ENGAGED

PARKING BRAKE VALVE

SECONDARY BRAKE VALVE

PARKING / SECONDARY BRAKE SWITCH

PARKING BRAKE RELEASE PUMP

PARKING BRAKE RELEASE VALVE

INVERTER VALVE TO TC LOCKUP VALVE AND HOIST PILOT SYSTEM

PARKING / SECONDARY BRAKE TANK

185 • Parking/secondary brake system

Shown is the parking/secondary brake hydraulic and air system with the secondary brakes RELEASED and the parking brakes ENGAGED. Supply air from the parking/secondary brake air tank flows to the secondary brake valve and is blocked from flowing to the inverter valve signal port. Supply air is allowed to flow through the inverter valve and is blocked by the parking brake air valve. No air pressure is present to move the spool in the parking brake release valve. Supply oil from the parking brake release pump is blocked by the spool. Oil from the parking brake is open to drain through the parking brake release valve, which allows the springs in the parking brake to ENGAGE the brakes.

• Parking/secondary brake switch input to Transmission/Chassis ECM

A parking/secondary brake switch is located in the air line between the parking brake valve and the parking brake release valve. The switch provides an input signal to the Transmission/Chassis ECM. When the parking or secondary brakes are ENGAGED, the switch signals the Transmission/Chassis ECM to allow rapid downshifts.

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4

5

2

1

6

3

3

186

1. Service brake and manual retarder relay valve 2. ARC relay valve 3. Double check valves 4. Brake cylinders • Relay valves reduce braking time • Double check valves separate systems

5. Pressure protection valve

6. Front brake slack adjuster

The front service brake relay valve (1) receives metered air from only the service brake valve or the manual retarder valve. The rear Automatic Retarder Control (ARC) brake relay valve (2) receives metered air from only the ARC valve. When the service brakes or manual retarder brakes are ENGAGED, the front relay valve opens and metered air flows from the service brake tank, through the double check valves (3), to the three brake cylinders (4). The brake relay valves reduce the time required to engage and release the brakes. The double check valves (3) are used to separate the service and manual retarder brakes from the ARC brake system. When the ARC brake system is ENGAGED, the rear relay valve opens and metered air flows from the service brake tank, through a pressure protection valve (5) and the double check valves (3), to the three brake cylinders (4). The pressure protection valve prevents a total loss of air pressure in the service brake air system if the ARC relay valve fails. The protection valve opens to send flow to the ARC relay valve at 380 kPa (55 psi) and closes when the pressure decreases below 310 kPa (45 psi). The brake cylinders operate by air-over-oil. When the metered air enters the brake cylinders, a piston moves down and pressurizes the oil in the bottom of the cylinders. One brake cylinder supplies oil to the front brakes through the slack adjuster (6). Two brake cylinders supply oil to the rear brakes through a separate slack adjuster.

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187

1. Brake oil makeup tank 2. Brake oil makeup tank supply screen

As the brake discs in the brake assemblies wear, more oil is needed from the brake cylinders to compensate for the wear. The brake makeup oil tank (1) supplies makeup oil for the brake cylinders. Oil from the parking brake release valve flows through an orifice and the screen (2) to provide a continuous supply of oil to the makeup tank. Low flow to the makeup tank can cause the makeup oil reserve to decrease and cause the brake cylinders to overstroke.

• Check brake makeup oil flow

To check for makeup oil flow, remove the cover from the makeup oil tank. With the engine at HIGH IDLE, a stream of oil filling the tank should be visible. If a stream of oil is not visible, the filter or hose to the tank may be restricted or pump flow may be low.

3. Brake overstroke switch

Keep the service brake ENGAGED for at least one minute. If air is in the system or a loss of oil downstream from the cylinders occurs, the piston in the cylinder will overstroke and cause an indicator rod to extend and open the brake overstroke switch (3). The switch provides an input signal to the Brake ECM. The Brake ECM sends the signal to the VIMS, which informs the operator of the condition of the service/retarder brake oil circuit. If an overstroke condition occurs, the problem must be repaired and the indicator rod pushed in to end the warning.

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4. Front brake oil pressure tap

Front brake oil pressure can be measured at the pressure tap (4) located on the front brake slack adjuster.

• Brake cylinder test

The oil-to-air ratio of the brake cylinder is approximately 6.6 to 1. To test the brake cylinder, install a gauge in the fitting on top of the brake cylinder and a gauge on the pressure tap on the slack adjuster. When the service brakes are ENGAGED, if the air pressure in the brake cylinder is 690 kPa (100 psi), the oil pressure measured at the slack adjuster should be approximately 4560 kPa (660 psi). When the brakes are RELEASED, both pressures should return to zero.

5. Brake cylinder breather

Inspect the condition of the breather (5) for the brake cylinders. Oil should not leak from the breathers. Oil leaking from the breathers is an indication that the oil piston seals in the brake cylinder need replacement. Air flow from the breathers during a brake application is an indication that the brake cylinder air piston seals need replacement.

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BRAKE CYLINDER BRAKES ENGAGED AIR PISTON

INDICATOR ROD

FROM MAKEUP TANK OIL PISTON

AIR INLET

TO SLACK ADJUSTER VALVE SPRING

ROD

188 • Brake cylinder ENGAGED

This slide shows a sectional view of the brake cylinder when the brakes are ENGAGED. Air pressure from the brake relay valve enters the air inlet. The air pressure moves the air piston and the attached rod closes the valve in the oil piston. When the valve in the oil piston is closed, the oil piston pressurizes the oil in the cylinder. The pressure oil flows to the slack adjuster.

• Overstroke switch indicates oil loss

If air is in the system or a loss of oil downstream from the cylinders occurs, the piston in the cylinder will overstroke, which causes the indicator rod to extend and open the brake overstroke switch. If an overstroke condition occurs, the problem must be repaired and the indicator rod pushed in to end the warning. When the air pressure is removed from behind the air piston, the spring moves the air piston and the attached rod opens the valve in the oil piston. Any makeup oil that is needed flows into the age at the top of the oil chamber, through the valve, and into the oil chamber at the right of the oil piston.

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189

1. Slack adjuster

The truck is equipped with two slack adjusters--one for the front brakes and one for the rear brakes. The slack adjuster (1) shown is for the rear brakes. The slack adjusters compensate for brake disc wear by allowing a small volume of oil to flow through the slack adjuster and remain between the slack adjuster and the brake piston under low pressure. The slack adjusters maintain a slight pressure on the brake piston at all times.

• Cooling oil pressure maintains clearance between discs

Brake cooling oil pressure maintains a small clearance between the brake discs.

2. Service brake pressure taps • Service brake bleed valves 3. Parking brake release pressure taps

The service brake oil pressure can be measured at the two taps (2) located on top of the slack adjusters. Air can be removed from the service brakes through two remote bleed valves (not shown) mounted on the rear axle housing. The parking brake release pressure can be measured at the two taps (3) on the axle housing. NOTE: Air can be removed from the front service brakes through bleed valves located on each wheel.

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BRAKE SLACK ADJUSTER

OIL FLOW TO BRAKE CYLINDER

SMALL PISTON LARGE PISTON

OIL FLOW FROM BRAKE CYLINDER

FROM WHEEL BRAKES

FROM WHEEL BRAKES

TO WHEEL BRAKES

TO WHEEL BRAKES

BRAKES ENGAGED

BRAKES RELEASED

190 • Slack adjuster RELEASED and ENGAGED • Large piston moves to ENGAGE brakes

• Small piston allows makeup oil to brakes

This slide shows sectional views of the slack adjuster when the brakes are RELEASED and ENGAGED. When the brakes are ENGAGED, oil from the brake cylinders enters the slack adjusters and the two large pistons move outward. Each large piston supplies oil to one wheel brake. The large pistons pressurize the oil to the service brake pistons and ENGAGE the brakes. Normally, the service brakes are FULLY ENGAGED before the large pistons in the slack adjusters reach the end of their stroke. As the brake discs wear, the service brake piston will travel farther to FULLY ENGAGE the brakes. When the service brake piston travels farther, the large piston in the slack adjuster moves farther out and s the end cover. The pressure in the slack adjuster increases until the small piston moves and allows makeup oil from the brake cylinders to flow to the service brake piston.

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• Brake springs move large pistons to center of slack adjuster

When the brakes are RELEASED, the springs in the service brakes push the service brake pistons away from the brake discs. The oil from the service brake pistons pushes the large pistons in the slack adjuster to the center of the slack adjuster. Makeup oil that was used to ENGAGE the brakes is replenished at the brake cylinders from the makeup tank.

• Large piston spring keeps pressure on service brake piston

The spring behind the large piston causes some oil pressure to be felt on the service brake piston when the brakes are RELEASED. Keeping some pressure on the brake piston provides rapid brake engagement with a minimum amount of brake cylinder piston travel.

• Check slack adjuster for correct operation

The slack adjusters can be checked for correct operation by opening the service brake bleed screw with the brakes RELEASED. A small amount of oil should flow from the bleed screw when the screw is opened. The small flow of oil verifies that the spring behind the large piston in the slack adjuster is maintaining some pressure on the service brake piston.

• Brakes ENGAGED-pressures should be equal

Another check to correct slack adjuster operation is to connect a gauge to the pressure tap on top of the slack adjuster and another gauge at the service brake bleed screw location. With system air pressure at maximum and the service brake pedal depressed, the pressure reading on both gauges should be approximately the same.

• Brakes RELEASED-residual pressure at bleed screw

When the brakes are RELEASED, the pressure at the slack adjuster should return to zero. The pressure at the service brake bleed screw location should return to the residual pressure held on the brakes by the slack adjuster piston. The residual pressures at the service brake bleed screw location should be:

• Check for warped brake discs

• Check for brake cooling oil leakage

785C front: 103 kPa (14.9 psi)

785C rear: 59 kPa (8.6 psi)

789C front: 106 kPa (15.3 psi)

789C rear: 65 kPa (9.5 psi)

Low residual pressure indicates a failed slack adjuster. High residual pressure may indicate a failed slack adjuster or warped brake discs. To check for warped brake discs, rotate the wheel to see if the pressure fluctuates. If the pressure fluctuates while rotating the wheel, the brake discs are probably warped and should be replaced. To check for brake cooling oil leakage, block the brake cooling ports and pressurize each brake assembly to a maximum of 138 kPa (20 psi). Close off the air supply source and observe the pressure trapped in the brake assembly for five minutes. The trapped pressure should not decrease.

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SERVICE/RETARDER BRAKE AIR SYSTEM SERVICE BRAKES ENGAGED

FRONT BRAKE COOLER DIVERTER VALVE

SERVICE BRAKE VALVE

SERVICE RELAY VALVE

PRESSURE PROTECTION VALVE

ARC RELAY VALVE

BRAKE LIGHT AND SERVICE / RETARDER SWITCH

RETARDER VALVE

ARC VALVE

RETARDER SWITCH

BRAKE CYLINDERS

191 • Service/retarder brake air system

This schematic shows the flow of air through the service/retarder brake air system when the retarder (manual and automatic) is RELEASED, and the service brakes are ENGAGED. Supply air pressure flows from the large service brake air tank to the relay valves and the service brake valve, manual retarder valve and the ARC valve. The manual retarder valve and the ARC solenoids block the flow of air. The service brake valve allows air to flow to two double check valves that block the ages to the manual retarder and ARC valves. Air pressure from the service brake valve flows through the double check valves to the service brake relay valve and the front brake oil cooler diverter valve.

• Relay valves reduce braking time • Double check valves separate systems

The service brake relay valve opens and metered air flows from the large service brake air tank to the brake cylinders. The relay valves reduce the time required to engage and release the brakes. A pair of double check valves above the brake cylinders prevent the flow of service brake air to the ARC relay valve.

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• Service brakes activate two switches

Air from the service brake valve also flows to the brake light switch and the service/retarder brake switch. Depressing the service brake pedal turns ON the brake lights and changes the transmission shift points and anti-hunt timer.

• Manual retarder operation

When the manual retarder lever is moved, air flows through three double check valves that block the ages to the service brake valve and the ARC valve. Air pressure from the manual retarder brake valve flows through the double check valves to the service brake relay valve and the front brake oil cooler diverter valve.

• Manual retarder activates three switches

Air from the manual retarder brake valve also flows to the retarder switch, the brake light switch and the service/retarder brake switch. Engaging the manual retarder turns ON the retarder dash lamp, the brake lights, and changes the transmission shift points and anti-hunt timer.

• ARC operation

When the ARC is activated, air flows through two double check valves that block the ages to the service brake valve and the manual retarder brake valve. Air pressure from the ARC valve flows through the double check valves to the front brake oil cooler diverter valve.

- Engages ARC relay valve

• Pressure protection valve prevents air loss

• ARC activates three switches

When the ARC brake system is ENGAGED, the ARC relay valve opens and metered air flows from the service brake tank, through a pressure protection valve and the double check valves, to the three brake cylinders. The pressure protection valve prevents a total loss of air pressure in the service brake air system if the ARC relay valve fails. The protection valve opens to send flow to the ARC relay valve at 380 kPa (55 psi) and closes when the pressure decreases below 310 kPa (45 psi). Air from the ARC valve also flows to the retarder switch, the brake light switch and the service/retarder brake switch. Engaging the ARC turns ON the retarder dash lamp, the brake lights, and changes the transmission shift points and anti-hunt timer.

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789C BRAKE COOLING SYSTEM

HOIST PUMP HOIST SCREENS

FRONT BRAKES

REAR BRAKES

HOIST VALVE FRONT BRAKE OIL COOLER

DIVERTER VALVE

OUTLET RELIEF VALVE INLET RELIEF VALVE

TORQUE CONVERTER CHARGING FILTER REAR BRAKE OIL COOLERS

PARKING BRAKE RELEASE VALVE

CONVERTER PARKING OUTLET BRAKE FILTER FILTER

192 • 789C brake oil cooling system: - Three pump sections for rear brakes - Two pump sections for front brakes • Rear brake cooling • Hoist pump flow

This schematic shows the flow of oil through the 789C brake cooling system. Three pump sections provide oil for rear brake cooling: the two sections of the hoist pump and the fourth section of the torque converter pump. Two pump sections provide oil for front brake cooling: the torque converter charging and the brake release sections of the torque converter pump. All the pumps pull oil from the hydraulic tank through suction screens. Oil flows from the hoist pump sections through two screens to the hoist valve. In the HOLD and FLOAT positions, oil from the pump flows through the hoist valve to the rear brake cooling system. Oil flows from the fourth section of the torque converter pump, s with the oil from the hoist valve, and flows to the rear brake oil coolers.

• Fourth section of TC pump flow

Oil from all three pump sections combines and flows through the screens and rear brake oil coolers located on the right side of the engine. The rear brake oil coolers are cooled by the engine jacket water cooling system. From the coolers, oil flows through the brakes and returns to the hydraulic tank.

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• Oil cooler relief valve for rear brake cooling

The pressure in the rear brake cooling system is controlled by the oil cooler relief valve located in the hoist valve. The relief valve setting is 790 kPa (115 psi).

• Front brake cooling

Oil flows from the torque converter charging pump through the torque converter charging filter, the torque converter, and the torque converter outlet screen to the front brake oil cooler diverter valve.

• Converter charging pump flow • Brake release pump flow

Oil flows from the brake release pump through the brake release filter to the brake release valve. The brake release valve controls the oil pressure to release the parking brakes, lock up the torque converter and shift the directional spool in the hoist valve. These functions require minimal oil flow. Most of the oil from the brake release pump flows through the brake release valve and s with the torque converter charging pump oil at the front brake oil cooler diverter valve.

• Front cooler used only with brakes ENGAGED

When the service or retarder brakes are ENGAGED, the front brake oil cooler diverter valve allows brake cooling oil to flow through the front brake oil cooler to the front brakes. When the brakes are RELEASED, the oil byes the cooler and flows directly to the brakes. The front brake oil cooler is cooled by the engine aftercooler cooling system. The aftercooler cooling system does not have temperature regulators (thermostats) in the circuit. Normally, front brake cooling oil is diverted around the cooler and goes directly to the front brakes. Diverting oil around the cooler provides lower temperature aftercooler air during high power demands (when climbing a grade with the brakes RELEASED, for example).

• 785C brake oil cooling system - Three pump sections for rear brakes - One pump section for front brakes

The brake cooling system on the 785C truck is slightly different from the 789C truck. The 785C truck does not have a fourth section on the torque converter pump for rear brake cooling. The parking brake release pump sends oil to the rear brake cooling system, not to the front brake cooling system.

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193

• Brake cooling oil pressure tap (arrow)

Shown is the left rear brake housing on a 789C truck. Brake cooling oil pressure can be tested at the two taps (arrow) located in the brake cooling oil tubes. One tap is located on the brake cooling inlet tube and another tap is located on the brake cooling outlet tube. The pressure measured at the brake inlet tube (from the oil coolers) will always be higher than the pressure measured at the brake outlet tube.

• Brake cooling oil pressure

With the brake cooling oil temperature between 79 to 93°C (175 to 200°F), the pressure measured at the brake inlet tube should be above 14 kPa (2 psi) at LOW IDLE and below 172 kPa (25 psi) at HIGH IDLE.

• High brake cooling oil temperature:

Four brake oil temperature sensors, one for each brake, are located in the brake oil cooling tubes. The brake oil temperature sensors provide input signals to the VIMS, which keeps the operator informed of the brake cooling oil temperature.

- Engine speed too low

The most common cause of high brake cooling oil temperature is operating a truck in a gear that is too high for the grade and not maintaining sufficient engine speed. Engine speed should be kept at approximately 1900 rpm during long downhill hauls.

- Slack adjuster pistons stuck

Also, make sure the pistons in the slack adjuster are not stuck and retaining too much pressure on the brakes (see Slides No. 189 and 190).

- Gear too high

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BRAKE ELECTRONIC CONTROL SYSTEM INPUT COMPONENTS PARKING BRAKE FILTER

CAT DATA LINK

SERVICE TOOL

BRAKE OVERSTROKE SWITCH

ENGINE ECM TRANSMISSION/CHASSIS ECM

BRAKE AIR PRESSURE

VIMS

LEFT BRAKE RELEASE PRESSURE

SHIFT LEVER SWITCH

RIGHT BRAKE RELEASE PRESSURE

THROTTLE SENSOR

ACTUAL GEAR SWITCH

ENGINE SPEED/TIMING SENSOR PARKING/SECONDARY BRAKE SWITCH

DIFFERENTIAL FILTER

TRANSMISSION OUTPUT SPEED SENSOR SERVICE/RETARDER BRAKE SWITCH

DIFFERENTIAL OIL TEMP SENSOR

OUTPUT COMPONENTS

DIFFERENTIAL PRESSURE DIFFERENTIAL OIL LEVEL

ARC ON INPUT

DIFFERENTIAL FAN RELAY

ENGINE OUTPUT SPEED SENSOR

ARC SUPPLY SOLENOID

ARC

ARC CONTROL SOLENOID

OFF INPUT RETARDER ARC ON/OFF PRESSURE SWITCH SWITCH AUTO RETARDER PRESSURE SWITCH

RETARDER ENGAGED LAMP

TCS

TCS ENGAGED LAMP

TCS TEST SWITCH

TCS TCS SELECTOR SOLENOID LEFT AND RIGHT

LEFT WHEEL SPEED SENSOR PROPORTIONAL (SERVO) SOLENOID

RIGHT WHEEL SPEED SENSOR

194 BRAKE ELECTRONIC CONTROL SYSTEM • Brake ECM

The "C" Series trucks use an additional Electronic Control Module (ECM) for controlling both the Automatic Retarder Control (ARC) and the Traction Control System (TCS). The Automatic Retarder Control (ARC) and the Traction Control System (TCS) control modules are replaced with one Brake ECM. The Brake ECM controls both the ARC and the TCS functions. The TCS is now on the CAT Data Link, and the Electronic Technician (ET) service tool can be used to diagnose the TCS.

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The Brake ECM receives information from various input components such as the Engine Output Speed (EOS) sensor, retarder pressure switch, left and right wheel speed sensors and the TCS test switch. Based on the input information, the Brake ECM determines whether the service/retarder brakes should ENGAGE for the ARC or the parking/secondary brakes should ENGAGE for the TCS. These actions are accomplished by sending signals to various output components. Output components include the ARC supply and control solenoids, the retarder ENGAGED lamp, the TCS selector and proportional solenoids and the TCS ENGAGED lamp. The Brake ECM also provides the service technician with enhanced diagnostic capabilities through the use of onboard memory, which stores possible diagnostic codes for retrieval at the time of service.

• Benefits of electronic communication

• Service tool functions

The Engine ECM, the Transmission/Chassis ECM, the Vital Information Management System (VIMS) and the Brake ECM all communicate through the CAT Data Link. Communication between the electronic controls allows the sensors of each system to be shared. The Electronic Control Analyzer Programmer (ECAP) and the Electronic Technician (ET) Service Tools can be used to perform several diagnostic and programming functions. Some of the diagnostic and programming functions that the service tools can perform are: - Display real time status of input and output parameters - Display the internal clock hour reading - Display the number of occurrences and the hour reading of the first and last occurrence for each logged diagnostic code and event - Display the definition for each logged diagnostic code and event - Display the supply and control solenoid engagement counter - Program the ARC control speed - Perform ARC diagnostic tests - new Flash files

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195

• Brake ECM (arrow): - No diagnostic window

The Brake ECM (arrow) is located in the compartment at the rear of the cab. The Brake ECM does not have a diagnostic window like the ARC and the TCS used on the "B" Series trucks.

- Diagnostics and programming require ECAP or ET

All diagnostic and programming functions must be performed with an Electronic Control Analyzer Programmer (ECAP) or a laptop computer with the Electronic Technician (ET) software installed. ET is the tool of choice because the Brake ECM can be reprogrammed with a "flash" file using the WinFlash application of ET. ECAP cannot "flash" files.

• Brake ECM looks like Engine ECM

The Brake ECM looks like the Engine ECM with two 40-pin connectors, but the Brake ECM does not have fittings for cooling fluid. Also, the Brake ECM has no access plate for a personality module.

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AUTOMATIC RETARDER CONTROL ENGINE SPEED SENSOR

BRAKE ECM (ARC/TCS) ON INPUT

ARC ON/OFF SWITCH OFF INPUT SERVICE TOOL ENGINE ECM TRANSMISSION/ CHASSIS ECM VIMS

CAT DATA LINK RETARDER ENGAGED LAMP

AIR FROM SERVICE BRAKE RESERVOIR

SUPPLY SOLENOID VENT

VENT CONTROL SOLENOID

SERVICE BRAKE VALVE

TO SERVICE / RETARDER BRAKE RELAY VALVE

AUTOMATIC RETARDER VALVE

MANUAL RETARDER VALVE

AUTO RETARDER PRESSURE SWITCH

RETARDER PRESSURE SWITCH

TO ARC RELAY VALVE

196 Automatic Retarder Control (ARC) • Automatic Retarder Control (ARC)

The Automatic Retarder Control (ARC) system function is to modulate truck braking (retarding) when descending a long grade to maintain a constant engine speed. The ARC system engages the service/retarder brakes. If the ON/OFF switch is moved to the ON position, the ARC will be activated if the throttle pedal is not depressed and the parking/ secondary brakes are RELEASED. The ARC system is disabled when the throttle is depressed or when the parking/secondary brakes are ENGAGED. The ARC is not connected to the service brakes and the manual retarder. When the ARC is ENGAGED, air flows from the ARC valve to a separate relay valve located near the brake master cylinders (see Slide No. 182).

STMG 706 11/98 • ARC set to maintain 1900 engine rpm

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The ARC is set at the factory to maintain a constant engine speed of 1900 ± 50 rpm (engine speed setting is programmable). When the ARC initially takes control of retarding, the engine speed may oscillate out of the ± 50 rpm target, but the engine speed should stabilize within a few seconds. For proper operation of the ARC, the operator needs only to activate the control with the ARC ON/OFF switch and select the correct gear for the grade, load, and ground conditions. The ARC is designed to allow the transmission to upshift to the gear selected by the shift lever. After the transmission shifts to the gear selected by the operator and the engine speed exceeds 1900 rpm, the ARC will apply the retarder as needed to maintain a constant engine speed.

• ARC provides engine overspeed protection

The ARC system also provides engine overspeed protection. If an unsafe engine speed is reached, the ARC will engage the brakes, even if the ARC ON/OFF switch is in the OFF position and the throttle is depressed. Trucks approaching an overspeed condition will sound a horn and activate a light at 2100 rpm. If the operator ignores the light and horn, the ARC will engage the retarder at 2180 rpm. If the engine speed continues to increase, the Transmission/Chassis ECM will either upshift (one gear only above shift lever position) or unlock the torque converter (if the shift lever is in the top gear position) at 2300 rpm.

• ARC provides programming and diagnostic capability

The ARC also provides service personnel with enhanced diagnostic capabilities through the use of onboard memory, which stores possible faults, solenoid cycle counts and other service information for retrieval at the time of service. By using an ECAP or a laptop computer with the Electronic Technician (ET) software installed, service personnel can access the stored diagnostic information or set the adjustable engine speed control setting. The Auto Retarder Control receives signals from several switches and sensors. The control analyzes the various input signals and sends signals to the output components. The output components are two solenoids and a lamp. INSTRUCTOR NOTE: For more detailed information about the Automatic Retarder Control (ARC) system, refer to the Service Manual Module "Automatic Retarder Control System" (Form SENR5683) and the Technical Instruction Module "Automatic Retarder Control System" (Form SEGV2593).

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1

2

197

1. Engine output speed sensor

2. Engine speed/timing sensor

• Use 8T5200 Signal Generator to simulate engine speed

Shown is the location of the Engine Output Speed (EOS) sensor (1) that provides the primary input signal used by the ARC. The engine speed information is the main parameter that the Brake ECM uses to control retarding. The engine speed sensor is a frequency sensor that generates an AC signal from the ing flywheel gear teeth. The engine speed/timing sensor (2) is also used by the ARC for diagnostic purposes. If the Brake ECM receives an input signal from the engine speed/timing sensor, but not the EOS sensor, the Brake ECM will log an engine speed fault. The ARC will not function without an engine speed signal from EOS sensor (1). NOTE: The 8T5200 Signal Generator/Counter Group can be connected to the engine speed sensor wiring harness and be used to simulate engine speed for diagnostic purposes. To connect the 8T5201 Signal Generator to the engine speed sensor wiring harness, fabricate jumper wires and connect the 8T5198 Adapter Cable (part of the 8T5200 Signal Generator/Counter Group) to the speed sensor harness Deutsch DT connector. 8T5198 Adapter

Deutsch DT Connector

Pin B Pin C

J765 BU Pin 2 (ground) 450 YL Pin 1 (signal)

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4 5

2

1 3

198

1. Retarder pressure switch

Shown is the location of the retarder pressure switch (1). The retarder pressure switch signals the Brake ECM when manual or automatic retarder air pressure is present. The switch is normally open and closes when the manual or automatic retarder is engaged. A fault is recorded when the Brake ECM detects the absence of retarder pressure (switch open) while the supply solenoid and the control solenoid are energized.

2. Auto retarder pressure switch 3. Automatic retarder valve

The auto retarder pressure switch (2) signals the Brake ECM when air pressure is present and the automatic retarder valve (3) is functioning. The auto retarder pressure switch is located in front of the cab in the output port of the automatic retarder valve. The switch is normally closed and opens only when the auto retarder is engaged. A fault is recorded when the Brake ECM detects the presence of auto retarder pressure (switch open) while the supply solenoid and the control solenoid are not energized.

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4. Supply solenoid valve

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The supply solenoid valve (4) turns ON or OFF to control the flow of supply air to the automatic retarder valve (3). The Brake ECM energizes the supply solenoid valve with +Battery voltage (24 Volts) at 100 rpm less than the programmed control speed setting. Normally, the reduced speed will be 1800 rpm, since the control speed is set to 1900 rpm at the factory. A fault is recorded if the Brake ECM senses the signal to the supply solenoid as open, shorted to ground, or shorted to battery.

5. Control solenoid valve

The control solenoid valve (5) modulates the air flow to the brakes during automatic retarding. The control solenoid receives a Pulse Width Modulated (PWM) signal from the Brake ECM. The longer the duty cycle, the more time the control solenoid valve is open, and more air pressure is allowed to the brakes. Voltage to the control solenoid increases proportionally from zero to approximately 22 Volts with the demand for more brake pressure. A fault is recorded if the Brake ECM senses the signal to the control solenoid as open, shorted to ground, or shorted to battery.

• Supply and control solenoid resistance

• ARC valve malfunction

Normal resistance through the supply and control solenoids is 31 Ohms. An excess resistance of approximately 40 Ohms will prevent the valves from opening and will cause a supply or control valve fault to be logged. Therefore, a measurement of approximately 71 Ohms or more will show that the solenoid is defective. The Brake ECM can also determine if the solenoid valves have malfunctioned (valves leaking). If air pressure is present at the auto retarder pressure switch when the solenoids are DE-ENERGIZED, the auto retarder pressure switch will signal the Brake ECM that the ARC valve has malfunctioned.

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TRACTION CONTROL SYSTEM BRAKE ECM (ARC/TCS) ELECTRONIC SERVICE TOOL TCS ENGAGED LAMP

SERVICE/RETARDER BRAKE SWITCH TRANSMISSION OUTPUT SPEED SENSOR

CAT DATA LINK

TCS SELECTOR SOLENOID LEFT AND RIGHT

TCS TEST SWITCH PROPORTIONAL SOLENOID

LEFT WHEEL SPEED SENSOR

+ 10V TO WHEEL SENSORS

RIGHT WHEEL SPEED SENSOR

199 Traction Control System (TCS) • TCS uses rear parking/secondary brakes

The Traction Control System (TCS) uses the rear parking/secondary brakes (spring engaged and hydraulically released) to decrease the revolutions of a spinning wheel. The TCS allows the tire with better underfoot conditions to receive an increased amount of torque. The system is controlled by the Brake ECM (see Slides No. 194 and 195). The Brake ECM monitors the drive wheels through three input signals: one at each drive axle, and one at the transmission output shaft. When a spinning drive wheel is detected, the Brake ECM sends a signal to the selector and proportional valves which ENGAGE the brake of the affected wheel. When the condition has improved and the ratio between the right and left axles returns to 1:1, the Brake ECM sends a signal to RELEASE the brake.

STMG 706 11/98 • TCS replaces AETA

• Service/retarder brake switch: - Stops TCS function - Performs diagnostic test

• Brake release pressure sensors

- 246 -

The TCS was formerly referred to as the Automatic Electronic Traction Aid (AETA). The operation of the system has not changed. The main differences are the appearance of the ECM, and the TCS is now on the CAT Data Link. Also, the ECAP and ET Service Tools can communicate with the TCS. A service/retarder brake switch (see Slide No. 128) provides an input signal to the TCS through the CAT Data Link and performs two functions: 1. When the service brakes or retarder are ENGAGED, the TCS function is stopped. 2. The service/retarder brake switch provides the input signal needed to perform a diagnostic test. When the TCS test switch and the retarder lever are ENGAGED simultaneously, the TCS will engage each rear brake independently. Install two pressure gauges on the TCS valve, and observe the pressure readings during the test cycle. The left brake pressure will decrease and increase. After a short pause, the right brake pressure will decrease and increase. The test will repeat as long as the TCS test switch and the retarder lever are ENGAGED. The TCS valve has a left and right brake release pressure sensor. A laptop computer with the ET software installed can also be used to view the left and right parking brake pressures during the test discussed above in function No. 2. When the proportional solenoid is ENERGIZED, ET will show 44% when the brake is FULLY ENGAGED. NOTE: During the diagnostic test, the parking/secondary brakes must be released.

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200

• Wheel speed sensor (arrow)

Shown is the right rear wheel speed sensor (arrow). The TCS monitors the drive wheels through three input speed signals: one at each drive axle, and one at the transmission output shaft.

• TOS sensor disables TCS

The Transmission Output Speed (TOS) sensor (see Slide No. 127) monitors the ground speed of the machine and provides input signals to the TCS through the CAT Data Link. The TCS uses the TOS sensor to disable the TCS when ground speed is above 19.3 km/h (12 mph).

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4

4

3

3

2

1

201 • TCS valve

1. Selector solenoid

The Traction Control System (TCS) valve is mounted inside the rear of the left frame rail. Two solenoids are mounted on the valve. Electrical signals from the Brake ECM cause the selector solenoid valve (1) to shift and select either the left or right parking brake. If the selector valve shifts to the left parking brake hydraulic circuit, the control oil is drained. The left reducing spool of the control valve can then shift and engage the parking brake. The Brake ECM energizes the selector solenoid valve with + Battery voltage (24 Volts). Normal resistance through the selector solenoid is between 18 and 45 Ohms.

2. Proportional solenoid

The proportional solenoid valve (2) controls the volume of oil being drained from the selected parking brake control circuit. The rate of flow is controlled by a signal from the Brake ECM. The proportional solenoid receives a Pulse Width Modulated (PWM) signal from the Brake ECM. The longer the duty cycle, the more time the proportional solenoid valve is open, and more oil pressure is drained from the brakes. Voltage to the proportional solenoid increases proportionally from zero to approximately 10 Volts with the demand for more braking. Normal resistance through the solenoid is between 12 and 22 Ohms.

3. Left and right brake release pressure taps 4. Left and right brake release pressure sensors

The pressure taps (3) or pressure sensors (4) can be used to check the left and right brake release pressures when performing diagnostic tests on the TCS. The pressure at the taps in the TCS valve will be slightly less than the brake release pressure measured at the wheels.

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TRACTION CONTROL SYSTEM (TCS) ENGINE RUNNING/BRAKES RELEASED TEST SWITCH SERVICE/RETARDER BRAKE SWITCH

LEFT DRIVE AXLE INPUT SIGNALS

BALL CHECK TRANSMISSION SPEED SENSOR

OUTPUT SIGNALS

ORIFICE

SCREEN

TCS ENGAGED LAMP SELECTOR SOLENOID PARKING BRAKE VALVE

RIGHT DRIVE AXLE PROPORTIONAL SOLENOID

202 • TCS operation with brakes RELEASED

Shown is the TCS with the engine running and the brakes RELEASED. When the machine is started: - Oil flows from parking brake release pump through the brake release oil filter where the flow is divided. One line from the filter directs oil to the parking brake release valve. The other line sends oil to the signal port (right end of signal piston) of the TCS control valve. - Oil flow to the TCS control valve signal port causes the ball check piston to move to the left and unseat the drain ball check valve. Opening the drain ball check valve opens a drain age to the hydraulic tank.

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When the operator releases the parking brakes: - Air pressure is increased at the parking brake release valve forcing the valve spool down. - Parking brake release oil can now flow through the parking brake release valve to the TCS control valve. - In the control valve, oil closes the parking/secondary ball check valve and flows through the screen. - Oil flows through the right and left brake control circuit orifices. - Oil flows to the ends of the left and right brake reducing valve spools. - When the control circuit pressure is high enough, the reducing spools shift toward the center of the TCS control valve and parking brake release oil flows to release the brakes.

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TRACTION CONTROL SYSTEM (TCS) ENGINE RUNNING/LEFT BRAKE ENGAGED TEST SWITCH SERVICE/RETARDER BRAKE SWITCH

LEFT DRIVE AXLE INPUT SIGNALS

BALL CHECK TRANSMISSION SPEED SENSOR

OUTPUT SIGNALS

ORIFICE

SCREEN

TCS ENGAGED LAMP SELECTOR SOLENOID PARKING BRAKE VALVE

RIGHT DRIVE AXLE PROPORTIONAL SOLENOID

203 • CS operation with left brake ENGAGED

Shown is the TCS with the engine running and the left brake ENGAGED. When signals from the sensors indicate that the left wheel is spinning 60% faster than the right wheel, the following sequence of events occurs: - The Brake ECM sends a signal to the selector solenoid valve and the proportional solenoid valve. - The selector solenoid valve opens a age between the outer end of the left brake pressure reducing valve and the proportional solenoid valve. - The proportional solenoid valve opens a age from the selector solenoid valve to drain. The proportional solenoid valve also controls the rate at which the oil is allowed to drain. - Control circuit oil drains through the selector valve and enters the proportional valve.

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- The reducing valve spool for the left parking brake shifts and blocks the flow of oil to the parking brake. - Oil in the left parking brake control circuit begins to drain. - The left parking brake begins to ENGAGE. - The left brake orifice restricts the flow of oil from the parking brake release valve. When the signals from the sensors indicate that the left wheel is no longer spinning, the following sequence occurs: - The Brake ECM stops sending signals to the selector solenoid and the proportional solenoid. - The selector solenoid valve and proportional solenoid valve block the age to drain and allow the control circuit pressure to increase. - The left brake reducing valve spool shifts to the center position and blocks the age to drain. - Parking brake release oil is directed to the left parking brake and the brake is RELEASED. INSTRUCTOR NOTE: For more detailed information on the Traction Control System (TCS) refer to the Service Manual module "Automatic Electronic Traction Aid" (Form SENR2986) and the Technical Instruction Module "Automatic Electronic Traction Aid" (Form SEGV2585).

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1

2

3

204

OPTIONAL EQUIPMENT FlexxaireTM Fan • Flexxaire fan: - Variable pitch - Temperature controlled

• Warms engine quickly • Reduces horsepower loss

1. Hub assembly 2. Coolant temperature sensor 3. Fan pitch actuator

Shown is a 3516B Engine with a FlexxaireTM Fan installed. The FlexxaireTM fan provides full control of air movement through the radiator with an automatically controlled, variable pitch fan. The fan is designed to help control cooling requirements in specific applications such as cold weather and high altitude. The thermostatic controller automatically adjusts the blade pitch to maintain an optimum engine coolant temperature. With zero-pitch start-up, the air dam effect prevents air flow through the radiator and the engine reaches the recommended operating temperature more quickly. The pitch will vary throughout the day based on the engine cooling temperature and air conditioning requirements. The automatic blade pitch control reduces the horsepower loss when engine cooling is not required. The 10 fan blades attach to the hub assembly (1). A coolant temperature sensor (2) and an air conditioning pressure sensor (see Slide No. 62) provide input signals to an electronic control box located behind the cab (see next page). The electronic control analyzes the input signals and sends an electrical signal to the actuator (3). The actuator rotates and changes the fan pitch as needed to increase or decrease the engine coolant temperature.

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1

3

4

2

205

1. Electronic control box 2. Remote display

• Control features

The FlexxaireTM Fan electronic control box (1) and the remote display (2) are located in the compartment behind the operator's station. The control box is used to set up and calibrate the Flexxaire fan. Remove the cover from the control box and follow the instructions on the label inside the cover. The FlexxaireTM control box provides many features. The customer must decide which features he wants to use before setting up the system. Some of the features are: Timed Auto-Purge, Purge Interval Override, Temperature Driven Auto-Purge: Off-highway Trucks normally PULL air through the radiator. For a PURGE to occur, the fan blades rotate and PUSH air through the radiator. Changing air flow direction can help clear debris from the radiator. Actuator Stall Detection: If the fan pitch actuator encounters excessive resistance (bolt falls into the linkage), the control will sense the increased current and attempt an automatic calibration. If the obstruction continues, as a safety measure, the control will rotate the fan blades to full pitch.

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Second Fluid Temperature Control: A second temperature sensor can be installed to control the fan pitch in addition to the engine coolant temperature sensor (brake oil temperature). Blaze Blocker: A fire suppression system can provide an input signal to the control that will rotate the fan blades to the NEUTRAL position. In the NEUTRAL position, the fan provides no air flow. Limiting the air flow reduces the amount of oxygen to the fire, and the fire suppressant is not blown from the engine compartment. • Fan setup requirements: - Actuator limits

- Temperature set points

2. Remote display 3. Air flow button - LED bar display

4. Purge button

The following two FlexxaireTM Fan Controls must be set up properly: Actuator Limits: This procedure sets the travel limits and the NEUTRAL position of the actuator. Temperature Set Point Calibration: This procedure sets the temperature range that the controller will try to maintain by changing the fan pitch. The remote display (2) can be used to change the air flow from PUSH to PULL by depressing the air flow button (3). The nine LED bar display to the right of the air flow button indicates the position of the fan. The bottom four LED's indicate the PULL direction. The center LED indicates the NEUTRAL position. The top four LED's indicate the PUSH direction. The purge button (4) will start the purge cycle if one has been programmed into the control (optional). INSTRUCTOR NOTE: More detailed information about the FlexxaireTM Fan System can be found in the Service Manual module "FlexxaireTM Fan Installation And Maintenance Manual" (Form SEBC1152).

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206

CONCLUSION This presentation has provided a basic introduction to the Caterpillar 785C and 789C Off-highway Trucks. All the major component locations were identified and the major systems were discussed. When used in conjunction with the service manual, the information in this package should permit the serviceman to analyze problems in any of the major systems on these trucks.

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SLIDE LIST 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45.

789C model view Right side 789C truck Front of 789C truck Truck body options Walk around inspection Maintenance checks Front wheel bearing Front suspension cylinder Air filter housing Right side engine Transmission charging filter Transmission hydraulic tank Final drive Differential oil level Safety cable Fuel tank Primary fuel filter Parking brake and torque converter Brake cylinder breathers Front air dryer 789C engine oil filters 785C engine oil filters Oil change connector Secondary fuel filters Engine shutdown switch Air filter restriction indicators 789C cooling system Air cleaner indicators Ether cylinders Batteries Lubrication tank Steering system tank Air tank drain valve Windshield washer reservoir Daily checks Operator's station Operator and trainer seats Hoist control lever Dash (left side) Operator controls Switches and signals Manual retarder lever Brake and throttle pedals Shift console Overhead switches

46/ 47. 48. 49. 50. 51. 52. 53. 54. 55. 56 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78 79. 80. 81. 82. 83. 84. 85. 86. 87. 88. 89.

Circuit breaker Center dash Rocker switches VIMS message center module VIMS interface modules VIMS main module VIMS diagnostic connector Electronic Technician (ET) 3516B engine model view Electronic control system component diagram Engine ECM Atmospheric pressure sensor Engine speed/timing sensor Throttle position sensor EUI fuel injector solenoid Input switches and sensors Air conditioner compressor switch Crankcase pressure sensor ECM logged events Additional ECM logged events Systems controlled by ECM Engine oil pre-lubrication Speed fan control Oil renewal system components Oil level switches Cooling system Radiator Water pump Coolant Engine (right side) Jacket water coolant flow Auxiliary (aftercooler) water pump Rear aftercooler temperature sensor 789C air charging system Lubrication system Oil filters 785C engine oil filters Engine oil system Primary fuel filter Fuel transfer pump Secondary fuel filters Fuel injectors Fuel system circuit Air induction and exhaust system

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SLIDE LIST 90. 91. 92. 93. 94. 95. 96. 97. 98. 99. 100. 101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112. 113. 114. 115. 116. 117. 118. 119. 120. 121. 122. 123. 124. 125. 126. 127. 128. 129. 130.

Turbocharger inlet pressure sensor 351B turbochargers Exhaust temperature sensor 3512B air induction and exhaust system Power train components Torque converter Torque converter (converter drive) Torque converter drive (direct drive) Torque converter pump (four sections) Torque converter charging filter Torque converter inlet relief valve Torque converter outlet screen Brake oil cooler and diverter valve Parking brake release valve Torque converter lockup clutch valve (iron) Torque converter lockup clutch control (direct drive) Torque converter hydraulic system Transfer gears Transmission lube supply hose Power shift planetary transmission Transmission pump Transmission scavenge screens Transmission charging filter Transmission oil cooler by valve and oil cooler Transmission charging pump Transmission clutch pressures ICM transmission controls (sectional view) Transmission hydraulic system Rear axle pump Pump supply hose Oil filter by switch Rear axle oil cooling and filter system Double reduction planetary gear final drives Transmission/Chassis ECM Transmission/Chassis electronic control system Shift lever switch Transmission gear switch Transmission Output Speed (TOS) sensor Service/retarder brake switch Body position sensor Steering system

131. 789C steering system (no steer/maximum flow 132 785C steering system (hold) 133. Steering tank and filter 134. 785C steering pump 135. 785C steering pump (maximum flow) 136. Pump compensator valve 137. 785C steering pump (minimum flow) 138. 789C steering pump 139. 789C steering pump supply oil 140. 789C steering pump operation (maximum flow) 141. 789C steering pump (low pressure standby) 142. Accumulator charging valve 143. Load sensing controller 144. 789C solenoid and relief valve manifold 145. 785C solenoid and relief valve manifold 146. Solenoid and relief valve manifold (sectional view) 147. 789C steering directional valve 148. Steering directional valve (no turn) 149. Steering directional valve (right turn) 150. 785C solenoid and relief valve manifold and crossover relief valves 151. 785C crossover relief system (external impact) 152. 789C Hand Metering Unit (HMU) 153. 789C steering accumulators 154. Shutdown control 155. Hoist control system 156. Hoist lever 157. Hoist control position sensor 158. Hoist, converter and brake tank 159. Hydraulic tanks (rear) 160. Two section hoist pump 161. Hoist screens 162. Pump supply ports 163. Counterbalance valve 164. Hoist control valve (hold) 165. Hoist control valve (raise) 166. Hoist counterbalance valve (raise, lower and float) 167. "C" Series hoist control valve (lower) 168. "C" Series hoist control valve (float)

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SLIDE LIST 169. 170. 171. 172. 173. 174. 175. 176. 177. 178. 179. 180. 181. 182. 183. 184. 185. 186. 187. 188. 189. 190. 191. 192. 193. 194. 195. 196. 197. 198. 199. 200. 201. 202. 203. 204. 205. 206.

Two-stage hoist cylinders Hoist system (hold) Air and brake systems Oil cooled brake assembly (cutaway) Air charging system 789C air dryers Service/retarder brake tank Pressure protection valve Automatic lubrication solenoid air valve Parking/secondary brake tank 789C air charging system Manual retarder valve Service brake valve Inverter valve signal port Brake release valve Normal parking and secondary brake operation Parking/secondary brakes released and parking brakes engaged Service brake and manual retarder relay valve Brake oil makeup tank Brake cylinder (engaged) Slack adjuster (iron) Slack adjuster (released and engaged) Service/retarder brake air system (engaged) 789C brake oil cooling schematic Brake cooling oil pressure tap Brake electronic control system Brake ECM (iron) Automatic Retarder Control (ARC) schematic Engine Output Speed (EOS) sensor Retarder pressure switch Traction Control System (TCS) schematic Wheel speed sensor Traction Control System (TCS) valve Traction Control System (TCS) operation (brakes released) Traction Control System (TCS) operation (left brake engaged) Flexxaire fan Flexxaire fan electronic control box Model rear view

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Serviceman's Handout No. 1

"C" SERIES TRUCK SERVICE TOOLS MAINTENANCE 2P8250 4C5084 4C9301 4C4911 1U9921 5P0957 5P3514 9U5617 7S5437 5P8610 1U5551 7S9394 7F8240 1P0545 6V4040 5P1720

Filter Strap Wrench Filter Cutting Tool Coolant Conditioner Test Kit Battery Load Tester Battery Post Cleaner Coolant and Battery Tester (°F) Coolant and Battery Tester (°C) Suspension oil fill unit Nitrogen Charging Group Nitrogen Charging Adapter (for charging two suspension cylinders) Valve Extension (for charging steering accumulators) Tire Fill Air Hose Tire Valve Repair Tool Tire Gauge Nitrogen Tire Inflation Kit Seal Pick

ENGINE 9U7400 9S9082 1U5470 1U5440 147-5482 147-2056 147-5537 148-7211 9U5132

Multitach II Group Engine Turning Tool Engine Pressure Gauge Group Fuel Flow Monitor Group (3400/3500) 3500/3500B Valve Lash Setting Group Dial Indicator (inches) (need with 147-5482) Dial Indicator (metric) (need with 147-5482) Bridge Nut Socket (need with 147-5482) Injector Height Tool Group

ELECTRONIC CONTROL DIAGNOSTICS Laptop Computer for VIMS and ET IBM Compatible Computer with DB-9 or DB-25 Pin RS-232 Serial Port Vital Information Management System (VIMS) JERD2093 Caterpillar Common Services Software JERD2137 VIMS Software License JERD2138 VIMS Software Subscription JERD2139 VIMS Software Subscription (additional copies) 127-9797 VIMS Computer to Truck Adapter Cable (same as TPMS)

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Serviceman's Handout No. 2

ELECTRONIC CONTROL DIAGNOSTICS (continued) Electronic Technician (ET) JEBD3003 ET Getting Started Book and CD JERD2124 Electronic Technician (ET) Software License JERD2129 ET Software Subscription (Engines and Machines) JERD2142 ET Software Subscription (Machines Only) 7X1700 Communication Adapter NEXG4523 Service Program Module (SPM) for Communication Adapter 139-4166 ET Universal Cable (connects Communication Adapter to machine; for CAT Data Link and ATA Communication) 7X1425 ET Adapter Cable (connects Laptop to Communication Adapter) 7X1695 Timing Probe Cable (for timing calibration) 6V2197 Timing Probe Magnetic Pickup (for timing calibration) 6V3093 Timing Probe Adapter Sleeve (for timing calibration) LERQ3133 HyperACCESS/5--Flash File Software

ELECTRICAL 4C3406 9U7246 1U5804 6V3000 1P2305 8T0900 146-4080 9U7330 8T3224 7X1710 4C9024 9U7560 5P4205 121-9587 4C4074

Deutsch Connector Kit (HD10 with crimp tool) Deutsch Connector Kit (DT no crimp tool) Deutsch Connector Crimp Tool (part of 4C3406) Sure Seal Repair Kit Terminal and Connector Repair Kit AC/DC Clamp-on Ammeter Digital Multimeter (reads PWM and Frequency) Fluke 87 Digital Multimeter (reads PWM and Frequency) Multimeter Probes (for checking CE connectors) Signal Reading Probe Group (spade slides in connectors) Service Tool and Soldering Iron Battery Field Soldering Iron Group (used with 4C9024) 5/32 T-handle Allen wrench for DRC connectors Deutsch Connector (HD10/DRC)--Blue removal tool CE Connector--Black removal tool

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Serviceman's Handout No. 3

POWER TRAIN 8T5200 6V4157 6V6064

Signal Generator (substitutes transmission/engine speed signals) Transmission/Hydraulic System Pressure Gauge Group Test Cover (top of ICM transmission)

TEMPERATURE MEASUREMENTS 4C6500 8T2844 4C6090 6V9130 8T5334 123-6700 148-2400

Digital Thermometer Group Temperature Recorder Stickers Multichannel Temperature Selector Group Temperature Adapter Group (for Digital Multimeter) Surface Temperature Probe Infrared Thermometer with Laser Sight Compact Infrared Thermometer with Laser sight

MISCELLANEOUS FT1114 7H1447 Vacuum Cap Assembly--7H1447 Hydraulic Cap FT1115 4J3754 Vacuum Cap Assembly--4J3754 Hydraulic Cap 5P0306 Transducer 6V4142 Open nipple 1/8-27 NPTF 5K5068 Pipe Nipple 1/8-27 x 1/8-27 NPTF male union 3B6488 Black Pipe Coupling 1/4-18 NPTF both ends 5P1750 to 5P1756 Thin plates slide in hose ends to block oil 5P1750 Blocker Plate 1.25 in ID Line 5P1756 Blocker Plate 4.00 in ID Line 6V7830 Tetragauge 1U5481 Pressure Gauge Group 1U5482 Pressure Adapter Group for 1U5481 4C4892 ORFS Fitting and Gauge Group 8T5320 Hydraulic Test Group (contains blocker plates) 5P1404 Adapter (7/8-14 male x 9/16-18 female) for brake bleed port 2P8421 Adapter (1 1/16-12 male x 9/16-18 female) for brake cooling pressure at hoist valve 1U5000 Auxiliary Power Unit (gas engine powered pump for dumping or towing) 1U5525 Auxiliary Power Unit Attachment Group 146-1738 Precision Borescope 1U8869 Digital Dial Indicator 6V6042 Dial Indicator Group 8T5096 Magnetic Dial Indicator Group 8T1000 Digital Positioner Group FT1975 Suspension Gauge Block Stop Watch

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Serviceman's Handout No. 4

785C/789C TRANSMISSION/CHASSIS ECM PIN IDENTIFICATION Pin Number J1- 1 J1- 2 J1- 3 J1- 4 J1- 5 J1- 6 J1- 7 J1- 8 J1- 9 J1-10 J1-11 J1-12 J1-13 J1-14 J1-15 J1-16 J1-17 J1-18 J1-19 J1-20 J1-21 J1-22 J1-23 J1-24 J1-25 J1-26 J1-27 J1-28 J1-29 J1-30 J1-31 J1-32 J1-33 J1-34 J1-35 J1-36 J1-37 J1-38 J1-39 J1-40

Chassis Control Function

Type Of Pin

Battery+ (24V) Battery- (ground) CAT Data LinkDash Body Up Lamp Battery- (ground) Battery+ (24V) Solenoid Return Start Relay CAT Data Link+ Secondary Steering Relay Lockup Clutch Solenoid Upshift Solenoid Transmission Charge Filter Switch Shift Lever 1 Switch and Sensor Ground Return Switch and Sensor Ground Return Unused Downshift Solenoid Shift Lever 4 Transmission Lube Filter Switch Location code 1 (open) Location code 0 (grounded) Shift Lever Ground Shift Lever 2 Service Brake Pressure Switch Secondary Brake Pressure Switch Shift Lever 5 ECM Location Enable (+Battery) Transmission Gear 1 Transmission Gear 2 Transmission Gear 3 Transmission Gear 4 Transmission Gear 5 Unused Shift Lever 3 Transmission Gear Ground Low Steering Pressure Switch Location Code 2 (open) Hoist Screen Switch Key Switch Input

Power Power CAT Data LinkProportional Driver No. 2 Power Power Solenoid Return ON/OFF Driver No. 13* CAT Data Link+ Proportional Driver No. 1 Proportional Driver No. 4 Proportional Driver No. 11 Switch To Ground 8 Switch To Ground 16 Switch and Sensor Ground Switch and Sensor Ground Proportional Driver No. 3 Proportional Driver No. 12 Switch To Ground 7 Switch To Ground 3 Switch To Ground 26 Switch To Ground 25 Switch To Ground 6 Switch To Ground 2 Switch To Ground 12 Switch To Ground 13 Switch To Ground 28 Switch To Battery 3 Switch To Ground 4 Switch To Ground 1 Switch To Ground 10 Switch To Ground 14 Switch To Ground 29 Switch To Battery 2 Switch To Ground 5 Switch To Ground 15 Switch To Ground 11 Switch To Ground 27 Switch To Ground 9 Switch To Battery 1*

* The J1-8 driver receives power from the J1-40 input.

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Serviceman's Handout No. 5

785C/789C TRANSMISSION/CHASSIS ECM PIN IDENTIFICATION Pin Number J2- 1 J2- 2 J2- 3 J2- 4 J2- 5 J2- 6 J2- 7 J2- 8 J2- 9 J2-10 J2-11 J2-12 J2-13 J2-14 J2-15 J2-16 J2-17 J2-18 J2-19 J2-20 J2-21 J2-22 J2-23 J2-24 J2-25 J2-26 J2-27 J2-28 J2-29 J2-30 J2-31 J2-32 J2-33 J2-34 J2-35 J2-36 J2-37 J2-38 J2-39 J2-40

Chassis Control Function

Type Of Pin

Hoist Enable Relay Unused Solenoid Return Transmission Oil Temperature Sensor Unused T/C Oil Temperature Sensor Float Solenoid Autolube Solenoid Unused Unused Hoist Lever +8V Sensor Power Supply Raise Solenoid Unused +10V Sensor Power Supply Unused Unused Body Position Sensor/Body Up Switch Lower Solenoid Unused Unused Unused Engine Output Speed Unused Unused Unused Unused Neutral Output Unused Unused Unused Unused Unused Body Raise Output Converter Output Speed Unused Back-up Alarm Transmission Output Speed Unused Low Steering Warning Output

Proportional Driver No. 6 Proportional Driver No. 8 Solenoid Return PWM 4/Switch To Gnd 33 PWM 2/Switch To Gnd 31 PWM 6/Switch To Gnd 35 Proportional Driver No. 5 Proportional Driver No. 7 No Connection PWM 5/Switch To Gnd 34 PWM 1/Switch To Gnd 30 +8V Sensor Power Supply Proportional Driver No. 10 Timer In No. 4 +10V Sensor Power Supply No Connection No Connection PWM 3/Switch To Gnd 32 Proportional Driver No. 9 Unused No Connection Open Collector Output 3 Timer In No. 2 Unused Unused No Connection No Connection Open Collector Output 1 No Connection Timer In No. 3Q Timer In No. 4Q No Connection No Connection Open Collector Output 4 Timer In No. 3 Unused ON/OFF Driver No. 14 Timer Input No. 1 No Connection Open Collector Output 2

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Serviceman's Handout No. 6

785C/789C BRAKE CONTROL PIN IDENTIFICATION Pin Number J1- 1 J1- 2 J1- 3 J1- 4 J1- 5 J1- 6 J1- 7 J1- 8 J1- 9 J1-10 J1-11 J1-12 J1-13 J1-14 J1-15 J1-16 J1-17 J1-18 J1-19 J1-20 J1-21 J1-22 J1-23 J1-24 J1-25 J1-26 J1-27 J1-28 J1-29 J1-30 J1-31 J1-32 J1-33 J1-34 J1-35 J1-36 J1-37 J1-38 J1-39 J1-40

Chassis Control Function

Type Of Pin

Battery+ (24V) Battery- (ground) CAT Data LinkRetarder Lamp Battery- (ground) Battery+ (24V) Solenoid Return TCS Dash Lamp CAT Data Link+ TCS Right Brake On/Off Solenoid TCS Left Brake On/Off Solenoid ARC Control Solenoid ARC On/Off Switch N/O when Off ARC On/Off Switch N/C when Off Switch and Sensor Ground Return Switch and Sensor Ground Return TCS Proportional Servo Valve ARC Supply Solenoid TCS System Test Switch ARC Pressure Switch Location Code 1 (grounded) Location Code 0 (open) Retarder Switch Unused Brake Cooling Filter Switch (793C only) Brake Overstroke Switch Unused ECM Location Enable (+Battery) Unused Unused Rear Diff Level Switch Rear Diff Filter Switch Park Brake Filter Switch Unused Unused Unused Unused Location Code 2 (open) Unused +Battery Input

Power Power CAT Data LinkProportional Driver No. 2 Power Power Solenoid Return ON/OFF Driver No. 13* CAT Data Link+ Proportional Driver No. 1 Proportional Driver No. 4 Proportional Driver No. 11 Switch To Ground 8 Switch To Ground 16 Switch and Sensor Ground Switch and Sensor Ground Proportional Driver No. 3 Proportional Driver No. 12 Switch To Ground 7 Switch To Ground 3 Switch To Ground 26 Switch To Ground 25 Switch To Ground 6 Switch To Ground 2 Switch To Ground 12 Switch To Ground 13 Switch To Ground 28 Switch To Battery 3 Switch To Ground 4 Switch To Ground 1 Switch To Ground 10 Switch To Ground 14 Switch To Ground 29 Switch To Battery 2 Switch To Ground 5 Switch To Ground 15 Switch To Ground 11 Switch To Ground 27 Switch To Ground 9 Switch To Battery 1*

* The J1-8 driver receives power from the J1-40 input.

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Serviceman's Handout No. 7

785C/789C BRAKE CONTROL PIN IDENTIFICATION Pin Number J2- 1 J2- 2 J2- 3 J2- 4 J2- 5 J2- 6 J2- 7 J2- 8 J2- 9 J2-10 J2-11 J2-12 J2-13 J2-14 J2-15 J2-16 J2-17 J2-18 J2-19 J2-20 J2-21 J2-22 J2-23 J2-24 J2-25 J2-26 J2-27 J2-28 J2-29 J2-30 J2-31 J2-32 J2-33 J2-34 J2-35 J2-36 J2-37 J2-38 J2-39 J2-40

Chassis Control Function

Type Of Pin

Rear Diff Fan High Solenoid Unused Solenoid Return Left Brake Retract Pressure Sensor Right Brake Retract Pressure Sensor Rear Diff Oil Pressure Sensor Unused Unused Unused Rear Diff Oil Temperature Sensor Brake System Air Pressure Sensor +8V Sensor Power Supply Unused Unused +10V Sensor Power Supply Unused Unused Unused Unused Unused Unused Unused RR Wheel Speed Sensor Unused Unused Unused Unused Unused Unused Unused Unused Unused Unused Unused Engine Speed Sensor Unused Rear Diff Fan Low Solenoid LR Wheel Speed Sensor Unused Unused

Proportional Driver No. 6 Proportional Driver No. 8 Solenoid Return PWM 4/Switch To Gnd 33 PWM 2/Switch To Gnd 31 PWM 6/Switch To Gnd 35 Proportional Driver No. 5 Proportional Driver No. 7 No Connection PWM 5/Switch To Gnd 34 PWM 1/Switch To Gnd 30 +8V Sensor Power Supply Proportional Driver No. 10 Timer In No. 4 +10V Sensor Power Supply No Connection No Connection PWM 3/Switch To Gnd 32 Proportional Driver No. 9 Unused No Connection Open Collector Output 3 Timer In No. 2 Unused Unused No Connection No Connection Open Collector Output 1 No Connection Timer In No. 3Q Timer In No. 4Q No Connection No Connection Open Collector Output 4 Timer In No. 3 Unused ON/OFF Driver No. 14 Timer Input No. 1 No Connection Open Collector Output 2

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Serviceman's Handout No. 8

MODULE IDENTIFICATION CODES MID 36 27 116 49 57 58

ELECTRONIC CONTROL Engine ECM Transmission/Chassis ECM Brake ECM or Automatic Retarder Control (ARC) or Traction Control System (TCS) VIMS Main Module Interface Module No. 1 Interface Module No. 2

FAILURE MODE IDENTIFIER LIST FMI 00 01 02 03 04 05 06 07 08 09 10 11 12 13

FAILURE DESCRIPTION Data valid but above normal operational range Data valid but below normal operational range Data erratic, intermittent or incorrect Voltage above normal or shorted high Voltage below normal or shorted low Current below normal or open circuit Current above normal or grounded circuit Mechanical system not responding properly Abnormal frequency, pulse width or period Abnormal update Abnormal rate of change Failure mode not identifiable Bad device or component Out of calibration

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Serviceman's Handout No. 9

ELECTRONIC UNIT INJECTION (EUI) ENGINE (MID 36) COMPONENT and SIGNAL CODES

CID

FMI

01 01 02 02 03 03 04 04 05 05 06 06 07 07 08 08 09 09 10 10 11 11 12 12 13 13 14 14 15 15 16 16

F05 F06 F05 F06 F05 F06 F05 F06 F05 F06 F05 F06 F05 F06 F05 F06 F05 F06 F05 F06 F05 F06 F05 F06 F05 F06 F05 F06 F05 F06 F05 F06

DESCRIPTION Cylinder 1--Open Circuit Cylinder 1--Short Cylinder 2--Open Circuit Cylinder 2--Short Cylinder 3--Open Circuit Cylinder 3--Short Cylinder 4--Open Circuit Cylinder 4--Short Cylinder 5--Open Circuit Cylinder 5--Short Cylinder 6--Open Circuit Cylinder 6--Short Cylinder 7--Open Circuit Cylinder 7--Short Cylinder 8--Open Circuit Cylinder 8--Short Cylinder 9--Open Circuit Cylinder 9--Short Cylinder 10--Open Circuit Cylinder 10--Short Cylinder 11--Open Circuit Cylinder 11--Short Cylinder 12--Open Circuit Cylinder 12--Short Cylinder 13--Open Circuit Cylinder 13--Short Cylinder 14--Open Circuit Cylinder 14--Short Cylinder 15--Open Circuit Cylinder 15--Short Cylinder 16--Open Circuit Cylinder 16--Short

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Serviceman's Handout No. 10

ELECTRONIC UNIT INJECTION (EUI) ENGINE (MID 36) COMPONENT and SIGNAL CODES CID

FMI

91 100 100 100 101 101 101 110 110 168 168 168 190 190 190 190 248 253 254 261 262 262 263 263 267 268 273 273 273 273 273

F08 F03 F04 F13 F03 F04 F13 F03 F04 F00 F01 F02 F02 F03 F07 F08 F09 F02 F12 F13 F03 F04 F03 F04 F02 F02 F00 F01 F03 F04 F13

DESCRIPTION Throttle Output Signal--Abnormal Oil Pressure Signal--Open/Short to +Battery Oil Pressure Signal--Open/Short to Ground Oil Pressure Sensor--Calibration Crankcase Pressure Signal--Open/Short to +Battery Crankcase Pressure Signal--Open/Short to Ground Crankcase Pressure Sensor--Calibration Coolant Temperature Signal--Open/Short to +Battery Coolant Temperature Signal--Open/Short to Ground Battery Voltage--Above Normal Battery Voltage--Below Normal Battery Voltage--Intermittent Engine Speed/Timing Signal--Lost/Erratic Engine Speed/Timing Signal--Open/Short to +Battery Engine Speed/Timing Sensor--Misinstalled Engine Speed/Timing Signal--Abnormal CAT Data Link--Communication Error Personality Module Mismatch Internal ECM Problem Speed/Timing Sensor--Calibration Analog Supply--Short to +Battery Analog Supply--Short to Ground Digital Supply--Short to +Battery Digital Supply--Short to Ground Ground Level Shutdown Inputs--Incorrect Check Programmable Parameters Turbocharger Outlet Pressure Signal--Above Normal Turbocharger Outlet Pressure Signal--Below Normal Turbocharger Outlet Pressure Signal--Open/Short to +Battery Turbocharger Outlet Pressure Signal--Short to Ground Turbocharger Outlet Pressure Sensor--Calibration

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Serviceman's Handout No. 11

ELECTRONIC UNIT INJECTION (EUI) ENGINE (MID 36) COMPONENT and SIGNAL CODES CID

FMI

274 274 274 275 275 275 276 276 276 291 291 296 338 338 338 526 526 542 542 542 544 545 545 546 546 569 569 800 827 828 829 829

F03 F04 F13 F03 F04 F13 F03 F04 F13 F05 F06 F09 F05 F06 F11 F05 F06 F03 F04 F13 F08 F05 F06 F05 F06 F05 F06 F09 F08 F08 F03 F04

DESCRIPTION Atmospheric Pressure Signal--Open/Short to +Battery Atmospheric Pressure Signal--Short to Ground Atmospheric Pressure Sensor--Calibration Right Turbocharger Inlet Pressure Signal--Open/Short to +Battery Right Turbocharger Inlet Pressure Signal--Short to Ground Right Turbocharger Inlet Pressure Sensor--Calibration Left Turbocharger Inlet Pressure Signal--Open/Short to +Battery Left Turbocharger Inlet Pressure Signal--Short to Ground Left Turbocharger Inlet Pressure Sensor--Calibration Engine Fan Solenoid--Open Circuit Engine Fan Solenoid--Short to Ground CAT Data Link Communications Error with Transmission Control Pre-lubrication Relay--Open Circuit Pre-lubrication Relay--Short to Ground Pre-lubrication Relay--Timeout Wastegate Solenoid--Open Circuit (793 only) Wastegate Solenoid--Short to Ground (793 only) Unfiltered Oil Pressure Signal--Open/Short to +Battery Unfiltered Oil Pressure Signal--Short to Ground Unfiltered Oil Pressure Sensor--Calibration Engine Fan Speed Signal--Abnormal Ether Injection START Relay--Open/Short to +Battery Ether Injection START Relay--Short to Ground Ether Injection HOLD Relay--Open/Short to Ground Ether Injection HOLD Relay--Short to +Battery Oil Renewal Solenoid--Open/Short to +Battery Oil Renewal Solenoid--Short to Ground VIMS Communications Error Left Exhaust Temperature Abnormal Right Exhaust Temperature Abnormal Rear Aftercooler Temperature Signal--Open/Short to +Battery Rear Aftercooler Temperature Signal--Short to Ground

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Serviceman's Handout No. 12

TRANSMISSION/CHASSIS ECM (MID 27) COMPONENT and SIGNAL CODES CID

FMI

168 177 177 190 248 269 269 378 378 378 444 444 444 590 590 627 627 672 700 701 701 701 702 704 704 707 707 707 708 708 708

F01 F03 F04 F02 F09 F00 F01 F03 F05 F06 F03 F05 F06 F09 F12 F03 F04 F02 F02 F02 F08 F11 F02 F03 F04 F03 F05 F06 F03 F05 F06

DESCRIPTION System Voltage--Low Transmission Oil Temperature Sensor--Open/Shorted to +Battery Transmission Oil Temperature Sensor--Shorted to Ground Engine Output Speed (EOS) Signal--Lost/Erratic CAT Data Link Communication Error Sensor Power Supply--Shorted to +Battery Sensor Power Supply--Shorted to Ground Auto Lube Solenoid (grease)--Shorted to +Battery Auto Lube Solenoid (grease)--Open Auto Lube Solenoid (grease)--Shorted to Ground Start Relay--Short to +Battery Start Relay--Open Circuit Start Relay--Short to Ground Engine Control Module--Missing on Data Link Engine Control Module--Device Bad Parking/Secondary Brake Pressure Switch--Open/Short to +Battery Parking/Secondary Brake Pressure Switch--Short to Ground Converter Output Speed (COS) Signal--Lost/Erratic Transmission Gear Switch--Invalid Transmission Output Speed (TOS) Signal--Lost Transmission Output Speed (TOS) Signal--Erratic Transmission Output Speed (TOS) Signal--Not Identifiable Gear Selector Lever--Invalid Service Brake Pressure Switch--Open/Short to +Battery Service Brake Pressure Switch--Short to Ground Upshift Solenoid--Shorted to +Battery Upshift Solenoid--Open Upshift Solenoid--Shorted to Ground Downshift Solenoid--Shorted to +Battery Downshift Solenoid--Open Downshift Solenoid--Shorted to Ground

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Serviceman's Handout No. 13

TRANSMISSION/CHASSIS ECM (MID 27) COMPONENT and SIGNAL CODES CID

FMI

709 709 709 724 724 724 725 725 725 773 773 800 800 826 826 967 967 1175 1175 1236 1236 1326

F03 F05 F06 F03 F05 F06 F03 F05 F06 F03 F04 F09 F12 F03 F04 F02 F09 F03 F06 F03 F06 F02

DESCRIPTION Lockup Solenoid--Shorted to +Battery Lockup Solenoid--Open Lockup Solenoid--Shorted to Ground Hoist Raise Solenoid--Shorted to +Battery Hoist Raise Solenoid--Open Hoist Raise Solenoid--Shorted to Ground Hoist Lower Solenoid--Shorted to +Battery Hoist Lower Solenoid--Open Hoist Lower Solenoid--Shorted to Ground Hoist Lever Sensor--Open/Shorted to +Battery Hoist Lever Sensor--Shorted to Ground VIMS--Missing on Data Link VIMS--Device Bad Torque Converter Oil Temperature Sensor--Open/Shorted to +Battery Torque Converter Oil Temperature Sensor--Shorted to Ground Machine Application Identity--Erratic Machine Application Identity--Missing on Data Link Body Position Sensor--Open/Shorted to +Battery Body Position Sensor--Shorted to Ground Body Up Dash Lamp--Short to +Battery Body Up Dash Lamp--Short to Ground Location Code--Incorrect

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Serviceman's Handout No. 14

BRAKE ECM (MID 116) AUTOMATIC RETARDER CONTROL (ARC) TRACTION CONTROL SYSTEM (TCS) COMPONENT and SIGNAL CODES CID

FMI

DESCRIPTION

84 84 91 100 168 190 190 190 248 269 269 296 541 541

F02 F09 F09 F03 F01 F02 F08 F09 F09 F00 F01 F09 F03 F04

Ground Speed Signal--Lost/Erratic Ground Speed Signal--Missing on Data Link Throttle Sensor--Missing on Data Link Engine Speed Cross Check--Incorrect System Voltage--Low Engine Output Speed (EOS) Signal--Lost/Erratic Engine Output Speed (EOS) Signal--Abnormal Engine Output Speed (EOS) Signal--Missing on Data Link CAT Data Link--Communication Error Sensor Power Supply--Shorted to +Battery Sensor Power Supply--Shorted to Ground Transmission Control--Missing on Data Link Differential (Axle) Oil Pressure Sensor--Open/Shorted to +Battery Differential (Axle) Oil Pressure Sensor--Shorted to Ground

607 608 627 689 689 689 690 690 690 700 702 704 710 710 710 710

F02 F02 F09 F03 F05 F06 F03 F05 F06 F09 F09 F09 F03 F05 F06 F12

Left Rear Wheel Speed Sensor Signal--Lost/Erratic Right Rear Wheel Speed Sensor Signal--Lost/Erratic Parking/Secondary Brake Pressure Switch--Missing on Data Link TCS Left Solenoid--Shorted to +Battery TCS Left Solenoid--Open TCS Left Solenoid--Shorted to Ground TCS Right Solenoid--Shorted to +Battery TCS Right Solenoid--Open TCS Right Solenoid--Shorted to Ground Transmission Gear Switch--Missing on Data Link Gear Selector Lever--Missing on Data Link Service/Retarder Brake Pressure Switch--Missing on Data Link ARC Supply Solenoid--Shorted to +Battery ARC Supply Solenoid--Open ARC Supply Solenoid--Shorted to Ground ARC Supply Valve--Malfunction

STMG 706 11/98

- 274 -

Serviceman's Handout No. 15

BRAKE ECM (MID 116) AUTOMATIC RETARDER CONTROL (ARC) TRACTION CONTROL SYSTEM (TCS) COMPONENT and SIGNAL CODES CID

FMI

711 711 711 711 711 712 712 713 713 714 715 719 719 719 966 966 796 796 796 800 835 835 849 849 967 967 1225 1225 1226 1226 1326

F03 F05 F06 F07 F12 F03 F06 F03 F04 F03 F03 F03 F05 F06 F03 F06 F03 F05 F06 F09 F03 F04 F03 F04 F02 F09 F03 F04 F03 F04 F02

DESCRIPTION ARC Control Solenoid--Shorted to +Battery ARC Control Solenoid--Open ARC Control Solenoid--Shorted to Ground ARC Control Valve--Mechanical Response Malfunction ARC Control Valve--Malfunction Retarder Dash Lamp--Shorted to +Battery Retarder Dash Lamp--Shorted to Ground ARC ON/OFF Switch--Open or Shorted to +Battery ARC ON/OFF Switch--Shorted to Ground ARC Pressure Switch--Open or Shorted to +Battery Retarder Pressure Switch--Open or Shorted to +Battery TCS Proportional Solenoid--Shorted to +Battery TCS Proportional Solenoid--Open TCS Proportional Solenoid--Shorted to Ground TCS Dash Lamp--Shorted to +Battery TCS Dash Lamp--Shorted to Ground Differential Fan HI Solenoid--Shorted to +Battery Differential Fan HI Solenoid--Open Differential Fan HI Solenoid--Shorted to Ground VIMS--Missing on Data Link Differential (Axle) Oil Temperature Sensor--Open/Shorted to +Battery Differential (Axle) Oil Temperature Sensor--Shorted to Ground System Air Pressure Sensor--Open/Shorted to +Battery System Air Pressure Sensor--Shorted to Ground Machine Application Identity--Erratic Machine Application Identity--Missing on Data Link Left Park Brake Oil Pressure Sensor--Open/Shorted to +Battery Left Park Brake Oil Pressure Sensor--Shorted to Ground Right Park Brake Oil Pressure Sensor--Open/Shorted to +Battery Right Park Brake Oil Pressure Sensor--Shorted to Ground Location Code--Incorrect

STMG 706 11/98

- 275 -

Serviceman's Handout No. 16

VIMS KEYPAD OPERATIONS The keypad allows the operator or a service technician to interact with the VIMS. Some of the functions that can be performed by the keypad are: PAYCONF PAYCAL TOT RESET SVCLIT SVCSET TEST MSTAT LUBSET LUBMAN EACK ESTAT ELIST EREC ERSET

7292663 729225 868 73738 782548 782738 8378 67828 582738 582626 3225 37828 35478 3732 37738

DLOG DLRES LA UN ODO

3564 35737 52 86 636

BLT CON

258 266

Configure Payload Monitor Calibrate Payload Monitor Show Payload Cycle Resettable Totals Reset Displayed Data Reset Service Light Service Light Set Self Test Instrumentation Show Machine Statistics (source and configuration codes) Set Lube Cycle Times Manual Lube Show Acknowledged Events (Active) Show Event Statistics Show Event List (Intermittent) Start Event Recorder Configure 1 Event Recorder (requires VIMS PC connection) Start/Stop Data Logger Reset Data Logger Change Language Change Units Odometer Set/Reset (requires VIMS PC connection) Change Backlight Change Display Contrast

OK Key: Used to complete keypad entries and to acknowledge events. Acknowledging an event will remove the event from the display temporarily. Severe events cannot be acknowledged. GAUGE Key: Displays parameters monitored by the VIMS. Depressing the arrow keys will scroll through the parameters. Entering the parameter number and the GAUGE key selects that parameter. F1 Key: Provides additional information on the current event being displayed. For MAINTENANCE events, the MID, CID, and FMI are displayed. For DATA events, the current parameter value is displayed (temperature, pressure, rpm).

SESV1706 11/98

Printed in U.S.A.