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Foreword

The descriptions and service procedures contained in this manual are based on designand method studies up to July 1996.

The products are under continuous development. Vehicles and components producedafter the above date may therefore have different specifications and repair methods.When this is believed to have a significant bearing on this manual, supplementary servicebulletins will be issued to cover the changes.

The new edition of this manual will update the changes.

In service procedures where the title incorporates an operation number, this is areference to an S.R.T. (Standard Repair Time).

Service procedures which do not include an operation number in the title are for generalinformation and no reference is made to an S.R.T.

The following levels of observations, cautions and warnings are used in this ServiceDocumentation:

Note:Indicates a procedure, practice, or condition that must be followed in order to havethe vehicle or component function in the manner intended.

Caution:Indicates an unsafe practice where damage to the product could occur.

Warning:Indicates an unsafe practice where personal injury or severe damage to theproduct could occur.

Danger:Indicates an unsafe practice where serious personal injury or death couldoccur.

Volvo GM Heavy TruckGreensboro, NC USA

Order number: PV776-TSP25323/1

1996 Volvo GM Heavy Truck, Greensboro, NC USA

All rights reserved. No part of this publication may be reproduced, stored in

retrieval system, or transmitted in any forms by any means, electronic, me-chanical, photocopying, recording or otherwise, without the prior written

permission of Volvo GM Heavy Truck.

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Contents

General .................................................................................................... 2

About This Manual ................................................................................ 2

Specifications ......................................................................................... 3

............................................................................................................... 3

Design and Function ............................................................................. 7

Air Brake System ..................................................................................... 7

General .................................................................................................. 7

Air Tubing and Fittings .......................................................................... 8

Air Tubing Repair ................................................................................ 10

Foldout A Brake Schematic, 4x2

Foldout B Brake Schematic, 6x4

Foldout C Supply System Routing

Foldout D Front Brake System Routing

Foldout E Rear Brake System Routing

Foldout F Parking Brake System Routing

Foldout G Trailer Brake System Routing

Foldout H Accessories System Routing

Foldout I Cab Air Tubing Routing

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Group 56 About This Manual

General

W5000485

About This ManualThis manual is intended to give information for helpingin troubleshooting the brake and air systems from pointto point without having to trace the actual tubing. Exceptfor foldouts A and B, each foldout describes a particular

circuit with its valves and actuators as located in thevehicle. Foldouts A and B describe the complete brakesystem schematically.

This manual should be used together with Service Manu-alsAir Brake Valves and Componentsand Compressorsand Air Dryerswhich describe each component in detailtogether with specifications, troubleshooting and test pro-

cedures.

2

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Group 56 Specificatio

SpecificationsGeneral

Type ............................................................................................................................................ Compressed air brake

Working pressure ......................................................................................................... 760 to 895 kPa (110 to 130 ps

Variants:

4X2, tractor4X2, truck6X4, tractor6X4, truck

Air Tubing and Fittings

TUBING

Material ................................................................................................................................................ Nylon (polyamide

Standard .................................................................................................................................. SAE J844 & FMVSS 10

Sizes:

Unreinforced ................................................................................................................................................. 1/4 in. O

Reinforced with fiber filament ............................................................................................ 3/8, 1/2, 5/8 and 3/4 in. OD

Safety factor, minimum ............................................................................................................................................ 5.3:System working pressure, maximum ................................................................................................ 1030 kPa (150 ps

System working temperature range ................................................................................ -40 to +90

C (-40 to +200

F

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Group 56 Specifications

FITTINGS

Type Thread Tube size Part number

Straight, thread to tube.Cyl. threads with O-ring seal.

M12x1.5M10x1.5M12x1.5

1/4 in.1/4 in.3/8 in.

807735883979658397850

Straight, thread to tube.Pipe threads. 1/2-14 NPTF1/2-14 NPTF1/2-14 NPTF3/8-18 NPTF3/8-18 NPTF3/8-18 NPTF3/8-18 NPTF1/4-18 NPTF1/4-18 NPTF1/4-18 NPTF1/8-27 NPTF

5/8 in.1/2 in.3/8 in.5/8 in.1/2 in.3/8 in.1/4 in.1/2 in.3/8 in.1/4 in.1/4 in.

83977288397727839772683977258397724839772383977228397721839772083977198397718

Straight, tube to tube. N/AN/AN/A

1/4 to 1/4 in.3/8 to 3/8 in.1/2 to 1/2 in.

807933680793378079338

Straight, tube to tube.Bulkhead (at pedal plate).

Plugs for bulkhead fitting.

N/AN/A

N/AN/A

1/4 in.3/8 in.

1/4 in.3/8 in.

83978918397851

80771868077187

90

, thread to tube. 1/8-27 NPTF1/8-27 NPTF1/4-18 NPTF1/4-18 NPTF1/4-18 NPTF3/8-18 NPTF3/8-18 NPTF

3/8-18 NPTF3/8-18 NPTF1/2-14 NPTF1/2-14 NPTF1/2-14 NPTF1/2-14 NPTF

1/4 in.3/8 in.1/4 in.3/8 in.1/2 in.1/4 in.3/8 in.

1/2 in.5/8 in.3/8 in.1/2 in.5/8 in.3/4 in.

8397697839769883976998397700839770183977028397703

839770483977058397706839770783977088076767

90

, thread to tube(Hex grip around base)


3/8-18 NPTF1/2-14 NPTF1/2-14 NPTF

1/4 in.1/4 in.3/8 in.1/2 in.1/4 in.3/8 in.

1/2 in.3/8 in.1/2 in.

839777083977718397772839777383977748397775

839777683977778397778

4

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Group 56 Specificatio

FITTINGS

Type Thread Tube 1 Part Number

45

, thread to tube. 1/8-27 NPTF1/8-27 NPTF1/4-18 NPTF1/4-18 NPTF


1/4 in.3/8 in.1/4 in.3/8 in.

1/2 in.3/8 in.1/2 in.3/8 in.1/2 in.3/4 in.

8397709839771083977118397712

839771383977148397715839771683977178076768

Thread Tube 1 Tube 2

Branch Tee, thread to tube and tube. 1/8-27 NPTF1/4-18 NPTF1/4-18 NPTF1/4-18 NPTF1/4-18 NPTF1/4-18 NPTF3/8-18 NPTF3/8-18 NPTF3/8-18 NPTF3/8-18 NPTF1/2-14 NPTF1/2-14 NPTF1/2-14 NPTF1/2-14 NPTF

1/4 in.1/4 in.1/4 in.3/8 in.1/4 in.1/2 in.3/8 in.1/4 in.1/2 in.5/8 in.1/4 in.3/8 in.1/2 in.5/8 in.


83977298397730839773183977328397733839773483977358397736839773783977388397739839774083977418397742

Branch Tee, thread to tube - tube.(Hex grip around base).

1/8-27 NPTF1/8-27 NPTF1/8-27 NPTF1/4-18 NPTF1/4-18 NPTF

1/4-18 NPTF3/8-18 NPTF3/8-18 NPTF1/2-14 NPTF1/2-14 NPTF

1/8 in.1/4 in.3/8 in.1/4 in.3/8 in.

1/2 in.3/8 in.1/2 in.3/8 in.1/2 in.

1/8 in.1/4 in.3/8 in.1/4 in.3/8 in.

1/2 in.3/8 in.1/2 in.3/8 in.1/2 in.

83978498397779839785283977808397781

83977828397783839778483977858397786

Branch Tee, 90

, thread to tube - tube. 1/4-18 NPTF3/8-18 NPTF1/2-14 NPTF1/2-14 NPTF1/2-14 NPTF1/2-14 NPTF1/2-14 NPTF

1/4 in.1/2 in.1/2 in.3/8 in.1/2 in.5/8 in.5/8 in.

1/4 in.1/2 in.3/8 in.1/2 in.1/2 in.1/2 in.5/8 in.

8397763839776483977658397766839776783977688397769

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Group 56 Specifications

FITTINGS

Type Thread Tube 1 Tube 2 Part Number

Run Tee, thread to tube - tube.(Tube 1 - straight; tube 2 - 90

).1/4-18 NPTF1/4-18 NPTF1/4-18 NPTF1/4-18 NPTF

1/4-18 NPTF3/8-18 NPTF3/8-18 NPTF3/8-18 NPTF3/8-18 NPTF3/8-18 NPTF3/8-18 NPTF3/8-18 NPTF1/2-14 NPTF1/2-14 NPTF1/2-14 NPTF1/2-14 NPTF1/2-14 NPTF1/2-14 NPTF

1/4 in.3/8 in.1/4 in.3/8 in.


1/4 in.1/4 in.3.8 in.3/8 in.


8397743839774483977458397746

83977478397750839775183977528397753839775483977558397756839775783977588397759839776083977618397762

Run Tee, thread to tube - tube.(Tube 1 - straight; tube 2 - 90

).(Hex grip around base).

1/8-27 NPTF1/4-18 NPTF1/4-18 NPTF1/4-18 NPTF3/8-18 NPTF3/8-18 NPTF1/2-14 NPTF1/2-14 NPTF

1/4 in.1/4 in.3/8 in.1/2 in.3/8 in.1/2 in.3/8 in.1/2 in.

1/4 in.1/4 in.3/8 in.1/2 in.3/8 in.1/2 in.3/8 in.1/2 in.

83977878397788839778983977908397791839779283977938397794

Tube 1 Tube 2 Tube 3

Branch Tee, tube to tube - tube. 1.4 in.3/8 in.1/2 in.

1/4 in.

1.4 in.3/8 in.1/2 in.

3/8 in.

1.4 in.3/8 in.1/2 in.

3/8 in.

839780483978058397806

8397927

Run Tee, tube to bulkhead to tube -tube (Used for stoplight switch).

1/4 in. 1/4 in. 1/4 in. 8079457

6

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Group 56 Design and Functi

Design and Function

Air Brake System

W5000581

123456789

CompressorGovernorAir DryerWet TankB System TankA System TankFoot ValveQuick Release ValveRelay Valve

10111213141516

ABS Modulator ValveSpring Brake ChamberFront Brake ChamberManifold Dash ValveQuick Release ValveTrailer Hand Brake ValveManifold Tractor Protec-tion Valve

17

181920

21

22

Low Air PressureSwitchAir Pressure GaugeAccessory ManifoldPressure ProtectionValveParking/Daytime Run-ning Light SwitchStop Light Switch

GeneralThe compressed air brake system is separated into twoparts: a supply system and a control system. The supplysystem produces, stores and supplies compressed airto the various brake valves in the system and to anyair powered accessories. The control system is on thedownside of an operating valve. The valve is regulatingthe amount of air going to an actuator or other valve. Mainoperating valves are Foot Valve(7), Trailer Hand BrakeValve(15) and Manifold Dash Valve(13). They regulateair pressure going to the wheel brake chambers whenoperated.

Other operating valves outside the brake system conneto the B system tank(5). A pressure protection valve(2protects the brake system from draining, should a probleoccur in an accessory supply line. A main supply line goto the cab, supplying air to cab components, and to taccessory manifold(19), located in the frame, supplyiair to chassis components.The circuit diagram above shows components for an ABbrake system. Components 9 and 10 change dependion application and vendor types. See Service Manual ABrake Valves and Componentsfor more information.

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Group 56 Design and Function

Air Tubing and FittingsThe foldouts represent the brake system as a schematiclayout or show actual routing in the vehicle. Foldouts Aand B are schematics of the entire brake system on a4x2 and a 6x4 vehicle. All other foldouts show the brakesystem valves and tubing in separate circuits. All color

on tubing and in the schematic layouts conform to thestandardized color scheme listed to the right.

The tubing in the foldouts are colored the same as the ac-tual tubing in the vehicle. This helps the identification andtroubleshooting process with less possibility for mistakes.

TUBING COLOR, PRIMARY

BLUE ...................................... Supply System CircuitRED ................................ Front Service Brake CircuitGREEN ............................ Rear Service Brake Circuit

ORANGE ................................. Parking Brake Circuit

TUBING COLOR, SECONDARY

BLUE (1/4 in.) ...................... Air Suspension ExhaustGREY (1/4 in.) ............................ Diff. Lock, InteraxleGREY (3/8 in.) ........................... Trailer Hand ControlBROWN (1/4 in.) ...................... Diff. Lock, InterwheelYELLOW (1/4 in.) ................ Fifth Wheel Air CylinderYELLOW (3/8 in.) ........ Compressor Supply; ExhaustORANGE (1/4 in.) ................ Bobtail Balance ControlBLACK (1/4 in.) .................. Air Seat; Options Supply

All tubing is made of nylon and sizes are always measuredas an outer diameter (OD). The 1/4 in. tubing is a solidcore, single ply extrusion. All other sizes are made ofa solid core, covered with a protective, colored layerwith fiber reinforcement between the layers. The coveris treated for heat and sunlight resistance.

W5000379

In areas where great flexibility is needed, air is routedin rubber hoses, for example, between frame and theaxles. A hose is built up of three layers of rubberand reinforcement. Hoses are specifically made for eachinstallation to the correct length with crimped on fittingson either end.

W5000384

Fittings are typically of the push-connect type. To connector disconnect tubing is very easy, which simplifies trou-bleshooting in the air system. New, simple test gaugeshave been introduced for testing the valves and pressures(See Service Manual: Air Valves and Components).

W5000377

The fitting body is made of brass. An internal O-ring seals

on the outside diameter of the tubing and the retainingcollar holds the tubing firmly in place. Straight fittings havean internal hex grip, most others have external hex grip.A number of valves also come with push-type connectorsalready installed in the valve body.

The fitting is designed for letting the tubing rotate toeliminate kinks. The fitting IS NOT designed for locationswith continuous movement, such as, between frame andaxle. Threads are pre-applied with sealant. A fitting canbe reused in the same port up to five times before newsealant needs to be applied.

W5000378

8

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Group 56 Design and Functi

Air Tubing InstallationTo ensure a tight seal between tubing and fitting, thetubing end needs to be cut straight. Also, inspect tubingthat has been removed for teethmarks around theperimeter where the retaining collar holds the tubing inplace. If the marks are too deep, that is, can be easilyseen or a depression can be felt by running a fingernail

across mark, recut the tubing before reinstalling.

W5000380

Installing is done by aligning tubing in a straight line withthe fitting opening. Push until the tubing stops against thebottom of the fitting.

W5000381

When the tubing has bottomed in the fitting, pull back tomake the collar retaining teeth engage the tubing. Do notpull too hard, only enough to ensure that the collar has

gripped the tubing.

W5000382

Air Tubing RemovalTo make removal easier, remove tubing when valve orcomponent is still in place.

WARNING

Always make sure that all compressed air is removedfrom the air system before removing tubing or compo-nents. Compressed air has great force and can createserious personal injury.

To disconnect, push the tubing into the fitting until itbottoms. Use release tool J42189 to push in the collarand then pull out tubing while holding the collar in.

W5000580

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Group 56 Design and Function

Air Tubing RepairIn the event that tubing has been severed as the resultof an accident or if tubing needs to be lengthened forrerouting, there are certain procedures that must befollowed.

In general, there are no restrictions against repairingtubing versus replacing it. A repaired tubing has the same

integrity as the rest of the system if the repairs are doneproperly. Tube to tube fittings are available for 1/4, 3/8and 1/2 in. tubing.

W5000582

Damage to one tube is repaired so that the repair fittingis close to a bracket for support. Prepare the tubing asoutlined on the previous page. Push the tubing ends intothe fitting. Leak test fitting at full pressure after systempressure has been established again.

W5000583

If a whole bundle of tubing needs to be repaired orlengthened, make sure the fittings are staggered insteadof installed at the same length. Put the larger fittings closeto a bracket for support and the smaller fittings furtheraway.

W5000584

10

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- Supply System Circuit

- Front Service Brake Circuit

- Rear Service Brake Circuit

- Parking Brake Circuit

- Trailer Supply

Supply

Operation

- Trailer Hand Control Circuit

1 Compressor2 Governor3 Air Dryer4 Wet Tank5 B System Tank6 A System Tank7 Foot Valve8 Quick Release Valve

9 Relay10 ABS 11 Sprin12 Front13 Mani14 Quic15 Traile16 Mani

1

10

10

18

18

17

17

12

12

8

7

This schematic describes the air brake system. All colorsare as they appear on the tubing in the vehicle. Componentsare grouped together so that the left of the schematic representsthe front of the vehicle and the right represents the rear of thevehicle. Other locations are not representative of true locationin the vehicle.

Use the schematic for troubleshooting and understanding the air

brake system function. To separate the supply and operationsystems, the operation system is shown with dashed lines. Inthe vehicle, all tubing is solidly colored.

Colors are to current standard ( see list on page 8 ) and areseparated into main groups, as listed:

This schematic describes the air brake system. All colorsare as they appear on the tubing in the vehicle. Componentsare grouped together so that the left of the schematic representsthe front of the vehicle and the right represents the rear of thevehicle. Other locations are not representative of true locationin the vehicle.Use the schematic for troubleshooting and understanding the airbrake system function. To separate the supply and operationsystems, the operation system is shown with dashed lines. Inthe vehicle, all tubing is solidly colored.Colors are to current standard see list on page 8 and areseparated into main groups, as listed:

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Foldout ABrake Schematic 4x2

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1 2

4

10

10

18

18

17

17

12

12

21

8

7

- Supply System Circuit

- Front Service Brake Circuit

- Rear Service Brake Circuit

- Parking Brake Circuit

- Trailer Supply Circuit

Supply

Operation

- Trailer Hand Control Circuit

1 Compressor2 Governor3 Air Dryer4 Wet Tank5 B System Tank6 A System Tank7 Foot Valve8 Quick Release Valve

9 Rela10 ABS11 Spri12 Fron13 Man14 Quic15 Trail16 Man

This schematic describes the air brake system. All colorsare as they appear on the tubing in the vehicle. Componentsare grouped together so that the left of the schematic representsthe front of the vehicle and the right represents the rear of thevehicle. Other locations are not representative of true locationin the vehicle.

Use the schematic for troubleshooting and understanding the airbrake system function. To separate the supply and operationsystems, the operation system is shown with dashed lines. Inthe vehicle, all tubing is solidly colored.

Colors are to current standard ( see list on page 8 ) and areseparated into main groups, as listed:

This schematic describes the air brake system. All colorsare as they appear on the tubing in the vehicle. Componentsare grouped together so that the left of the schematic representsthe front of the vehicle and the right represents the rear of thevehicle. Other locations are not representative of true locationin the vehicle.Use the schematic for troubleshooting and understanding the airbrake system function. To separate the supply and operationsystems, the operation system is shown with dashed lines. Inthe vehicle, all tubing is solidly colored.Colors are to current standard see list on page 8 ) and areseparated into main groups, as listed:

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1

Foldout BBrake Schematic 6x4

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WABCO

MIDLAND PURE AIR PLUS

123

1

2

3

CR TURBO 2000

1

2

3

BENDIX ADIP

12

3

4

1 - SUPPLY ( BLACK )2 - DELIVERY ( 5/8" BLUE )3 - CONTROL ( 1/2" BLUE )4 - FOR HOLSET COMPRS.ONLY

6 x 4

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Foldout CSupply System Routing

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6 x 4

4 x 2

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3

45

65

6

1817

7

Foldout DFront Brake System Routing

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ABS

4 x 2

6 x 4

ABS w/ ATC

RELAYVALVEREL YV LVE

ABS MODULATORVALVE BS MODUL TORV LVE

QUICK RELEASEVALVEQUICK RELE SEV LVE

TOBRAKE CHAMBERTOBR KE CH MBER

TOSPRING BRAKESTOSPRING BR KES

SPRING BRAKEBALANCESPRING BR KEB L NCEBOBTAILPROPORTIONBOBT ILPROPORTION

SUPPLYSERVICE

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Foldout ERear Brake Routing

65 65

13

6

2

6 A9 R11 S13 M14 Q21 P

5 B

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6 x 4

4 x 2

1

123

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55

7

1

Foldout FParking Brake Routing

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6 x 4

4 x 2

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1

2

5

( VOLVOONLY )

ENGINEBRAKE

FAN

HORN

201

512

Foldout GTrailer Brake System Routing

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See Foldout I

VOLVOTR NSMISSION

VEN ORTR NSMISSION

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5

1

20 19

Foldout HAccessories System Routing

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SEE BACK OFOLDOUT FO

TO AIR RIDE SEATS

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Foldout ICab Air Line Routing

INTERWHEEL

INTERAXLE

FIFTHWHEEL

AIRSUSPENSION

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Volvo Trucks North America, Inc.P.O. Box 26115, Greensboro, NC 27402-6115

Documents

PV776-TSP25323-1