BMW 1969-73 6 Cylinder Models Brake Repair Manual

Models Covered

• 2500 (1969-70)
• 2800 (1969-70)
• 2800 CS & CSA (1969-71)
• 3.0 CS & CSA (1969-71)
• Bavaria (1972-73)

DESCRIPTION

Models 2800 CS and CSA use ATE four-piston fixed caliper disc brakes on front and leading-trailing shoe drum brake on the rear. All other models use four wheel ATE disc brakes with four-piston caliper on front and two-piston caliper on the rear. All models use twin circuit, tandem piston master cylinders. Four wheel disc brake system use a pressure limiter to control hydraulic pressure applied to rear brakes. Hydraulic pressure to rear brakes is adjustable with the pressure limiter. Hand brake actuates cable to rear brake shoes. A special duo-servo drum-disc combination is used on rear wheels with disc brakes.

ADJUSTMENT

DRUM BRAKES 

2800 CS & CSA - Release handbrake, hoist vehicle and using suitable wrench (6038) loosen each brake shoe with its eccentric adjusting screw. While revolving wheel, turn left adjusting screw counterclockwise and right screw clockwise, until wheel will no longer turn. Loosen each screw ⅛ turn at a time until wheel turns freely.

DISC PADS

Front and rear disc brake assemblies are self-adjusting, therefore, no adjustment in service is required.

PARKING BRAKE

PISTON ALIGNMENT

Disc Brakes (With Integral Drum On Rear) - Release parking brake lever, raise and support vehicle and remove rear wheels. Insert brake adjusting tool through .6" hole in rotor. Turn start wheel adjuster until rotor can no longer be turned, then back off adjuster two or three teeth. Working inside driver compartment, tighten adjustment nut on hand lever until parking brake holds vehicle (before fifth ratchet stop is reached).

Models With Rear Drum Brakes - Drum brakes must be adjusted before attempting to adjust handbrake. Handbrake should be adjusted if hand operated lever can be pulled up more than five notches. Adjust with handbrake lever completely disengage, by turning adjuster on cable and next to hand brake lever. Adjustment is correct when handbrake will lock rear wheels without passing through more than four or five notches on ratchet.

HYDRAULIC SYSTEM BLEEDING

NOTE - Manufacturer recommends replacing brake fluid entire system once a year to avoid moisture build-up. Attach a pressure bleeder to master cylinder reservoir. CAUTION - Do not exceed 29 psi. Raise and support vehicle and remove wheels. Attach a bleeder hose to bleeder screw, and immerse opposite end of hose into a container partially filled with brake fluid. Open bleeder screw, allow all air has been expelled  from system. NOTE - On front wheel four piston calipers, bleed lower inboard screw before bleeding lower outboard screw.

REMOVAL AND INSTALLATION

DRUM BRAKE SHOES

Removal - Hoist vehicle, remove rear wheels and brake drums. Detach brake shoes from bottom support, then pull shoes out of wheel cylinders. Disconnect hand brake cable from rear shoes. Separate shoes by removing return springs.

Installation - Reverse removal procedure and note the following: Install long end of shoe push rod spring toward handbrake lever. Adjust brakes.

DISC PADS

Removal - Raise and support vehicle and remove wheels. Drive out retaining pins toward inside of vehicle and remove cross spring. Using a suitable extractor tool (3.9314-14002), remove disc pads from caliper assembly.

Installation - 1) NOTE -  Replacement of disc pads should be done in complete sets only. Using a cylinder brush, clean guide surface and support surface in caliper. Siphon sufficient fluid from outer cylinder reservoir to prevent overflowing, then press pistons to bottom of bores.

2) On rear two piston calipers, ensure machines position of piston face makes a 20° angle to lower caliper wall. Install disc pads, cross spring and retaining pins. After installation, depress brake pedal several times to position pads against rotor.

CALIPER ASSEMBLY

Removal - Remove master cylinder reservoir cap and plug fluid outlet lines. Raise and support vehicle and remove tire and wheel assembly. Disconnect hydraulic line(s), remove caliper mounting bolts, and separate caliper from caliper from backing plate.

Installation - Reverse removal procedure and bleed hydraulic system.
ROTOR
Removal & Installation (Front) - With caliper assembly removed, remove hub grease cap, cotter pin, and nut. Remove hub and rotor assembly. Remove Allen head bolts retaining rotor to hub and remove rotor. To install, reverse removal procedure, tighten all bolts and fittings evenly, and bleed hydraulic system if necessary. Adjust front wheel bearing. See Wheel Bearing Adjustment in WHEEL ALIGNMENT Section.
Removal & Installation (Rear) - Remove rear wheel and caliper assembly, then pull rotor out from axle shaft flange. To install, reverse removal procedure, tighten all bolts and fittings evenly, and bleed hydraulic system if necessary.
PARKING BRAKE SHOES
Removal - With rear caliper and rotor removed, disconnect lower return spring using brake spring pliers. Turn retaining springs 90 degrees using suitable tool (7014) and remove. Pull brake shoes apart at bottom and lift away upwards.
Installation - Reverse removal procedure and adjust parking brake shoes and cables.
MASTER CYLINDER
Removal - Remove master cylinder reservoir cap and plug fluid outlet lines. Remove hose fittings from master cylinder and raise above reservoir fluid level. Mark hydraulic lines for reassembly reference and disconnect from master cylinder. Remove nuts attaching cylinder to power unit, and separate master cylinder from power brake unit.

POWER UNIT PUSH ROD ADJUSTMENTS

Installation - Reverse removal procedure and note the following: Make sure rubber "O" ring seal between master cylinder and power unit is not damaged. Check clearance between power unit thrust rod and master cylinder piston with Plastigage and, if necessary, set to .020" by inserting a shim behind plunger head. Bleed hydraulic system and check for fluid leaks.
POWER BRAKE UNIT
Removal - 1) Remove air cleaner and battery, disconnect oil reservoir for power steering (if equipped) and move to one side. Block brake fluid reservoir outlets and remove hoses from master cylinder.
2) Remove lower left instrument panel housing and secure to one  side. Remove brake pedal clevis pin, and disconnect vacuum hose from intake manifold. Remove hydraulic lines from master cylinder marking positions for reassembly reference. Remove nuts retaining power unit to support and remove power unit.
Installation - Reverse removal procedure, bleed hydraulic system, and check following adjustments: Adjust length of piston rod (A) to 14.49-14.53". Adjust pedal height (B) to 9.65". Adjust exposed depth of brake light switch plunger (C) to .24-.28". See illustration.
Check Valve Replacement - Check valve is located in power unit vacuum line at intake manifold. To remove, loosen hose clamps, remove vacuum hoses, and remove valve. To install, reverse removal procedure, making sure arrow or block portion of valve faces intake manifold.
Filter Replacement - With power brake unit removed from vehicle, pull back rubber dust boot and remove retaining ring. Remove silencer and filter. To install, reverse removal procedure.
REAR BRAKE PRESSURE LIMITER
Removal & Installation - Plug fluid outlets in brake fluid reservoir. Disconnect brake hose and rear brake lines from pressure limiter. Remove mounting bolts and pressure limiter. To install, reverse removal procedure and bleed hydraulic system.

OVERHAUL

DRUM BRAKE WHEEL CYLINDER
Disassembly - With wheel brake drum removed, back off shoe adjusting cams, disconnect brake line and remove cylinder from backing plate. Disassemble wheel cylinder and pay particular attention to location and direction of parts.
Cleaning & Inspection - Clean all parts in alcohol or other suitable non oil base solvent. Discard all rubber parts and inspect all other parts for wear or damage.
Reassembly - Dip new parts in clean brake fluid or apply ATE cylinder paste. To install cylinder, reverse disassembly procedure and bleed brakes.
BRAKE CALIPER
Disassembly - With caliper removed from vehicle and disc pads remove from caliper, remove clamping rings and rubber protecting caps. Hold one piston in place using a suitable clamp, insert a piece of wood in caliper  cavity, then apply compressed air to fluid inlet and remove opposite piston. Remove sealing ring using a suitable plastic tool. Remove remaining piston(s) and seal(s) in same manner. NOTE - DO NOT separate caliper halves unless a leak is detected. To disassemble, remove expansion bolts, separate caliper halves and remove sealing rings.
Cleaning & Inspection - Clean all parts in alcohol and check for wear or damage; replace parts as necessary.
Reassembly - Reassemble caliper (if separated) using new seals and expansion bolts. Tighten expansion bolts from inside out. Coat pistons and caliper bores with ATE brake cylinder paste (or equivalent), install sealing rings, then install pistons into bores. Make sure pistons are not tilted when inserting. On two pison calipers, make sure machined surface of piston face makes a 20 degree angle to lower caliper wall. Install rubber protecting caps and clamp rings.
MASTER CYLINDER
Disassembly - Push in on primary piston and remove secondary piston stop screw. Remove snap ring from end of cylinder and remove primary and secondary piston assemblies and return spring. Disassemble piston assemblies noting number of parts used.
Cleaning & Inspection - Clean all parts in alcohol and inspect for wear or damage. NOTE - Cylinders with surface defects in bores must be replaced; do not overhaul.
Reassembly - Reassemble piston assemblies using a thin coating of ATE brake cylinder paste (or equivalent). Install piston assemblies into cylinder bore using a suitable guide sleeve (BMW 6063) to prevent damaging seals. Install secondary piston stop screw, making sure that piston is pushed fully forward before screw is installed and tightened. Install retaining ring in end of master cylinder bore.

BMW 1963-73 4 Cylinder Brakes Repair Manual

Models Covered

• 1600 (1966-71)
• 1600-2 (1966-71)
• 1800 (1963-66)
• 1800 Ti (1963-66)
• 2000 (1966-69)
• 2000 Ti & Tilux (1966-68)
• 2000 CS & CA (1966-67)
• 2002 (1968-73)
• 2002 Ti (1967-72)
• 2002 Tii (1972-73)

DESCRIPTION

Brakes on all models consist of ATE fixed caliper front disc brakes and leading-trailing shoe rear drum brakes. Disc calipers are either two or four piston units. All vehicles from 1970 onward, use tandem piston master cylinders. Hand brake system is operated by lever and cable, and attached to rear brake shoes.

ADJUSTMENT

FRONT DISC BRAKE PADS

Front dis brakes are self-adjusting, therefore, no adjustment in service is required.

REAR DRUM BRAKE SHOES

Raise and support rear of vehicle and release parking brake. Using an offset wrench (BMW 6038), tighten eccentric adjustment nuts while rotating wheel until wheel locks. Loosen adjusting nuts ⅛ turn or until wheel is just free to turn.

PARKING BRAKE

With rear brakes properly adjusted, pull rubber boot on parking brake lever and loosen lock nuts. Pull brake lever up to fifth ratchet stop and check for braking action at rear wheels. If adjustment is required, tighten adjusting nuts until rear wheels are locked. Tighten lock nuts and ensure wheels turn freely with parking brake lever released.

HYDRAULIC SYSTEM BLEEDING

NOTE - Manufacturer recommends replacement of brake fluid in entire system once a year to avoid moisture build-up. Attach a pressure bleeder to master cylinder reservoir. 

NOTE - DO NOT exceed 29 psi. Raise vehicle and remove front wheels. Attach a bleeder hose to bleeder screw and immerse opposite end of hose into a container of brake fluid. Open bleeder screw, allow all air to escape, then close bleeder screw. Continue operation until all air has been bled from system. NOTE - On front disc brakes, bleed lower inboard screw before bleeding lower outboard screw.

REMOVAL AND INSTALLATION

FRONT DISC BRAKE PADS

DISC PAD REMOVAL & INSTALLATION

Removal - Raise and support front of vehicle and remove wheels. Drive retaining pins out toward center of vehicle and remove cross spring. Using a suitable pulling tool (ATE 3.914-1800.2), remove brake pads. If pads are to be reinstalled, mark for reassembly reference. NOTE - Pads are not interchangeable.

Installation - NOTE - Replacement of disc pads should be done in complete sets only. Using a cylinder brush, clean guide surface and support surface in caliper. NOTE - DO NOT use oil based solvents. Siphon sufficient fluid from master cylinder reservoir to prevent overflowing, then press pistons to bottom of bores. Install disc pads, cross spring, and retaining pins. Pump brake pedal several times to position pads against rotor.

FRONT DISC BRAKE CALIPER

Removal - Raise and support front of vehicle and remove wheels. Disconnect hydraulic lines and plug openings. Remove bolts securing caliper to steering knuckle and remove caliper.

Installation - Reverse removal procedure and note the following: Left and right calipers are not interchangeable. When installed, bleeder screws must face upward. Tighten all bolts and fittings evenly and bleed hydraulic system.

FRONT DISC BRAKE ROTOR 

Removal - Remove caliper. NOTE - Do not allow caliper to hang from hydraulic line after removal; support out of way. Remove hub grease cap, cotter pin and nut, then remove hub and rotor assembly from axle. Remove Allen bolts and separate brake rotor from wheel hub. 

Installation - Install rotor onto wheel hub and tighten bolts securely. Install hub and rotor assembly onto axle, install outer wheel bearing, washer and nut. Adjust wheel bearings and install cotter pin and grease cap. See Wheel Bearing Adjustment in WHEEL ALIGNMENT Section. Install caliper and bleed hydraulic system if necessary.

REAR BRAKE DRUM

Removal - Remove tire and wheel assembly and loosen eccentric adjusting nuts. Pull drum straight out from axle to remove.

Installation - Install brake drum to axle, install tire and wheel assembly, and adjust brake shoes and parking brake (if required).

REAR BRAKE SHOES

REAR BRAKE ASSEMBLY

Removal (Exc. 1600-2 Models) - Hoist vehicle, remove rear wheels and brake drums. Detach brake shoes from bottom support, then pull shoes out of wheel cylinder. Disconnect hand brake cable from brake lever. Seperate brake shoes bye removing returning springs.

Removal 1600-2 Models - Release hand brake, hoist vehicle and remove cotter pin from axle castle nut. Remove wheel brake drum and axle flange as a unit. NOTE - If flange will not slide off axle, it will be necessary to remove wheel and drum from flange.

Installation (All Models) - Reverse removal procedure and adjust brake shoes. See Drum Brake Adjustment.

REAR BRAKE WHEEL CYLINDER

Removal - With brake drum removed, disconnect hydraulic line, and remove bleeder screw and wheel cylinder attaching bolts. Using on offset wrench (BMW 6038), turn brake shoe eccentric adjusting nuts until shoes are spread out from wheel cylinder as for as possible. Remove wheel cylinder maneuvering out of backing plate.

Installation - Reverse removal procedure and note the following: Make sure rubber "O" ring is installed on master cylinder between cylinder and power unit. Check clearance between master cylinder piston and power unit push rod. Clearance should be .020" and is adjusted by removing or installing shims behind head of power unit push rod.

POWER BRAKE UNIT

Removal - With master cylinder removed, disconnect power unit push rod from pedal assembly by removing clevis pin. Disconnect vacuum line from check valve, remove nuts attaching power unit to support, and remove power brake unit.

Installation - Reverse removal procedure, taking care to install rubber "O" ring on master cylinder between cylinder and power unit.

Check Valve Replacement - Vacuum check valve is located in vacuum line at intake manifold. To remove, loosen hose clamps, separate vacuum hoses from valve, and remove valve. To install, position check valve so that arrows or black portion of valve face intake manifold, install vacuum hoses, and install and tighten clamps.

Filter Replacement - With power brake unit removed from vehicle, remove rubber dust boot, retainer, silencer, and filter. To install, reverse removal procedure making sure slots in filter and silencer are offset 180° in relation to one another.

OVERHAUL

FRONT DISC BRAKE CALIPER
Disassembly - With caliper removed from vehicle, remove rubber protective caps, taking care not to damage pistons. Insert a piece of wood in caliper cavity, and remove pistons by applying compressed air to inlet holes of caliper. Using a plastic (or other soft material) tool, remove sealing rings from caliper bores. NOTE - Do not separate caliper halves unless a leak is detected. To disassemble caliper, remove expansion bolts and separate caliper halves. Remove sealing rings.
Cleaning and Inspection - Clean all parts in alcohol and dry with compressed air. Check cylinder bores, pistons and flange surfaces for rust, corrosion or other damage. Replace parts as necessary, do not attempt to machine caliper bores or pistons.
Reassembly - Reassemble caliper with new sealing rings and expansion bolts if halves were separated. Tighten caliper extension bolts alternately and evenly from inside out. Coat pistons and sealing rings with ATE brake cylinder paste (or equivalent) and install into caliper bores. Install protective caps.
REAR WHEEL CYLINDER 
Disassembly - Remove dust caps, then withdraw piston and seal assemblies and spring. Remove bleeder screw. Remove rubber seals from pistons.
Cleaning and Inspection - Clean all parts in alcohol. Check all parts for wear or damage; replace parts as necessary. Make sure that grooves on cylinder body are not corroded.

PRIMARY (REAR) PISTON ASSEMBLY

Reassembly - Coat all parts with ATE brake cylinder paste (or equivalent) and reverse disassembly procedure. NOTE - Manufacturer recommends replacing piston seals whenever cylinder has been disassembled.
MASTER CYLINDER
Disassembly - Push in on primary piston and remove piston stop screw on top of master cylinder. Remove retaining ring from end of cylinder and withdraw primary piston assembly. Use compressed air to remove secondary piston assembly from cylinder bore, then remove piston return spring. Disassemble piston assemblies, noting number and position of parts used.

SECONDARY (FRONT) PISTON ASSEMBLY

Cleaning and Inspection - Clean all parts in alcohol and check for wear or damage. NOTE - Cylinders with surface defects in bores must be replaced; do not overhaul.
Reassembly - Reassemble piston assemblies using a thin coating of ATE brake cylinder paste (or equivalent). Install piston assemblies into cylinder ore using a suitable guide sleeve (BMW 6063) to prevent damaging seals. Install secondary piston stop screw, making sure that piston is pushed fully forward before screw is installed and tightened. Install retaining ring in end of master cylinder bore.

Austin Marina 1973-75 Brake Repair Guide

DESCRIPTION

Brake system is hydraulically operated, utilizing dual piston and pad front disc brakes and rear wheel drum brakes. Drum brakes are single piston, sliding cylinder type. A dual piston master cylinder is used in conjunction with a Supervac power unit. Parking brake is hand operated and cable/lever actuated, operating the sliding wheel cylinder. A pressure differential warning valve is fitted to all vehicles to distribute hydraulic pressure evenly and to indicate pressure loss in system. Warning system is completed with a light on instrument panel that activates during pressure loss.

ADJUSTMENT

FRONT DISC BRAKES

No adjustment is required.

Fig. 1 Assembled View of Parking Brake Adjustment

REAR DRUM BRAKES

Raise rear of vehicle and block front wheels. Fully release parking brake and check that cables are not pulling on wheel cylinders. Turn adjuster screw in backing plate clockwise (viewed from center of vehicle) until brake drum cannot be turned. Loosen adjuster screw until wheel can just be turned.

PARKING BRAKE

With rear wheels properly adjusted, set parking brake lever on fourth ratchet tooth and check for braking effect on rear wheels. If braking effect is inadequate, loosen adjuster lock nut. Turn adjusting nut clockwise while holding cable sleeve from turning until correct adjustment is obtained. Tighten lock nut. Release parking brake lever and check that rear wheels rotate freely.

HYDRAULIC SYSTEM BLEEDING

1) Ensure rear wheel cylinder is free to slide on backing plate. Make sure all hydraulic fittings are tight and that wheel cylinder bleeder screws are closed. Fill master cylinder reservoir with brake fluid and make sure level is maintained throughout bleeding operation.

2) Attach bleeder tubes to bleeder screws on left-front and left-rear brakes, noting that bleeder screw on left-rear brake controls bleeding of both rear brakes. Commence bleeding with light strokes of pedal. NOTE - Do not push pedal through its entire stroke. Do not test pedal until system is fully bled.

3) Bleed right-front brake after all air has been expelled from left side of vehicle. If warning light should be activated during bleeding operation, continue bleeding until all air has been expelled from system. Determine which brake caused light to be activated.

Fig. 2 Front Disc Brake Assembly With Pads Removed

4) Attach a bleeder tube to a bleeder screw at opposite end of vehicle and open bleeder screw. Slowly depress pedal; or soon as light goes out, release pedal and tighten bleeder screw. Check fluid level in master cylinder reservoir and fill as necessary.

REMOVAL AND INSTALLATION

FRONT DISC BRAKE PADS

Removal  - Raise and support front of vehicle. Remove tire and wheel assembly. Remove spring clips and brake pad retaining pins. Remove brake pads and anti-squeal shims.

Installation - 1) Clean exposed end of piston and ensure that caliper is free of rust and dirt. Loosen bleeder screw and push pistons to base of cylinder. CAUTION - Level of fluid in master cylinder will rise. Siphon off sufficient fluid to prevent overflowing. Tighten caliper bleeder screw.

2) To complete installation, reverse removal procedure and note the following: Brake pads are interchangeable from side to side. Install anti-squeal shims with arrow pointing upwards, indicating forward direction of disc. With pads installed, pump brake pedal several times to reposition pistons. Bleed hydraulic system if necessary.

FRONT DISC BRAKE CALIPER

Removal - Raise and support front of vehicle. Remove tire and wheel assembly. Disconnect metal hydraulic line from flexible hose and from caliper. NOTE - Plug flexible hose to prevent loss of fluid. Remove caliper mounting bolts and remove caliper from vehicle.

Installation - To install, reverse removal procedure and note the following: Tighten caliper mounting bolts securely. Bleed hydraulic system.

FRONT DISC BRAKE ROTOR

Removal - Raise and support front of vehicle and remove tire and wheel assembly. Remove brake caliper. Remove grease cap, cotter pin, nut retainer, nut, and splined washer. Remove hub and rotor assembly. Remove four bolts retaining brake rotor to disc, and remove brake rotor.

Installation - 1) Install brake rotor onto hub, tightening retaining bolts securely. Install hub and rotor assembly onto axle and install bearing (if removed), splined washer, and nut. Spin hub and tighten nut to 5 ft. lbs. (.69 mkg). Loosen nut and then retighten finger tight.

2) Install nut retainer so that half of cotter pin hole is covered by one of the arms retainer. Loosen nut and retainer until cotter pin hole is fully uncovered, install cotter pin, and lock by turning legs of pin around nut retainer.

Fig. 3 Austin Marina Rear Drum Brake Assembly

3) CAUTION - Bearings must not be preloaded. Do not tighten nut so there is less than .001" (.025 mm) free play, measured with a dial indicator. To complete installation, reverse removal procedure.

REAR BRAKE DRUM

Removal & Installation - Raise and support rear of vehicle. Remove wheel and tire assembly. Remove two screws retaining drum to axle shaft flange. Loosen brake adjusting screw and remove brake drum. To install, reverse removal procedure and adjust brakes.

REAR BRAKE SHOES

Removal - With brake drum removed, disconnect cups and springs from anchor pins and remove pins. Disconnect return springs by lifting shoes from backing plate, disengaging front shoe from parking brake lever, and maneuvering shoes until spring tension is released.

Installation - Lightly coat shoe webs and anchor pins with Girling Brake Grease, taking care not to get any on shoe linings. Install return springs to shoes, engage parking brake lever into front shoe slotted web, and maneuver shoes into position on backing plate. Install anchor pins, springs and cups. Install drum and adjust brakes.

REAR WHEEL CYLINDER

Removal - With brake drum and shoes removed, disconnect flexible brake hose from metal line, plug metal line to prevent loss of fluid, and disconnect flexible line from wheel cylinder. Disconnect parking brake cable clevis from parking brake lever. Remove dust plate, retaining plate and spring clip, and remove cylinder from backing plate.

Installation - To install, reverse removal procedure and bleed hydraulic system.

MASTER CYLINDER

Removal - Disconnect master cylinder hydraulic lines at pressure differential warning valve and at master cylinder. Plug cylinder outlet parts and valve inlet parts to prevent loss of fluid. Remove nuts retaining master cylinder to power unit, and remove master cylinder.

Installation - To install, reverse removal procedure, tighten mounting nuts securely, and bleed hydraulic system., and note the following: Power unit operating rod must be retained to brake pedal lever with clevis pin installed in bottom hole of two holes in pedal lever.

PRESSURE DIFFERENTIAL WARNING VALVE

Removal - Disconnect battery and wiring to warning valve. Disconnect master cylinder-to-warning valve hydraulic lines, and disconnect warning valve-to-front and rear brake lines. Remove retaining bolts and remove warning valve.

Installation - To install, reverse removal procedure and bleed hydraulic system

Fig. 4 Exploded View of Disc Brake Caliper
and Pads

OVERHAUL

FRONT DISC BRAKE CALIPER

Disassembly - With caliper removed from vehicle, remove disc pads. Remove dust boot retaining rings and dust boots. Insert a piece of clean cloth between caliper pistons, then remove pistons by applying compressed air to fluid inlet part. Remove sealing rings from caliper. CAUTION - DO NOT  separate caliper halves.

Inspection - Clean all parts in Girling Cleaning Fluid or alcohol. Examine piston and caliper for scoring, corrosion or other wear; replace parts as necessary.

Reassembly - Lubricate all parts in clean brake fluid. Loosen bleeder screw. Install sealing rings inside caliper bores and press into seal grooves. Install dust boot on piston shoulder. Using a suitable tool (18G 590), press piston into caliper until .31" of piston is protruding. Install dust boot on cylinder shoulder and install retaining ring. Repeat procedure for remaining piston. Tighten bleeder screw and install brake pads.

Fig. 5 Disassembled Rear Wheel Cylinder

REAR WHEEL CYLINDER

Disassembly - With cylinder removed from vehicle, remove rubber dust boot and withdraw piston and seal assembly. Remove seal from piston. Clean all parts in Girling Cleaning Fluid or alcohol and inspect for wear or damage; replace parts as necessary.

Reassembly - Lubricate all parts with clean brake fluid. Using finger only, install new seal onto piston with lip of seal toward bottom of cylinder. Install piston and seal assembly into cylinder and install dust boot.

MASTER CYLINDER

Disassembly - 1) Separate fluid reservoir from master cylinder, then take out reservoir mounting seals. Clamp cylinder, then take out reservoir mounting seals. Clamp cylinder in a vice, push plunger down bore and withdraw secondary plunger stop pin.

2) Remove circlip from mouth of cylinder and withdraw primary plunger assembly using air pressure at secondary outlet port. Separate vacuum spring, seal retainer, seal and washer from primary plunger. Similarly, disassemble secondary plunger and note position of seals.

Inspection - Clean all parts in Girling Cleaning Fluid or alcohol and dry thoroughly. Check master cylinder bore. If not scored or ridged, new seals may be installed. If damaged, master cylinder must be replaced. Ensure that inlet and outlet ports are free from obstruction.

Fig. 6 Master Cylinder Reservoir, Body and Piston
Assembly

Reassembly - Reverse disassembly procedure following kit manufacturers instructions and incorporating the following: Press plunger into cylinder bore to facilitate secondary plunger pin reassembly. Secondary plunger return spring is larger of the two springs. Lubricate plunger return spring is larger of the two springs. Lubricate vacuum seals, spacers and plunger where necessary.

POWER UNIT

NOTE - Manufacturer does not recommend overhaul of power brake unit. However, a service kit consisting of a check valve, front seal and plate assembly, and filter may be installed once unit has been removed from vehicle.

Disassembly - Pull back dust cover over push and remove end cap and filter. From front of power unit, remove seal and plate assembly from shell recess, and remove check valve and grommet.

Fig. 7 Supervac Power Unit

Reassembly - Lubricate check valve grommet with Girling Grease and install into front shell. Install new  check valve into grommet. Coat new seal and plate assembly with Girling Grease and install into front shell, making sure that plate forces inward. Install new filter into neck of diaphragm plate and install new end cap. Install new dust cover over lugs of rear shell

Austin America 1968-71 Brakes Repair Manual

DESCRIPTION

All service brakes are hydraulically operated by pressure developed in tandem master cylinder. Front service brakes are of the sliding caliper disc brake type. Rear brake are internal-expanding, leading-trailing shoe type. Disc brakes function when single piston caliper, with two pads, contacts rotor. Pads simultaneously meet rotor because pressure forces one pad against rotor and induces caliper to slide, thereby bringing second pad into contact. Rear brakes operate when pressure on pedal expands shoes in drum, when pressure subsides, return springs retract lining to stops. An inertia valve is mounted on crossmember and is designed to prevent the possibility of rear wheel skidding. A steel ball inside body of valve holds open the valve allowing fluid passage. Under hard braking weight transfer causes ball to move and valve to close. A mechanical transfer causes ball to move and valve to close. A mechanical hand brake is actuated from inside vehicle and locks rear brake drums via cables and levers mounted on underbody and backing plates. Vehicle is equipped  with a hydraulic pressure failure switch which serves a stop light switch and hydraulic pressure loss indicator. Failure switch is located at four way hydraulic union. All models utilize a tandem master cylinder to develop hydraulic pressure. A vacuum servo unit (power brakes) is offered as optional equipment. Servo consists of three main components; a vacuum cylinder, air valve and slave cylinder.

ADJUSTMENT

DISC PAD NOTE - Frequent inspecting of disc pads is essential to maintain peak braking efficiency. If one exhibits extreme wear, change operating positions.

DRUM BRAKE NOTE - Adjustment is designed only to compensate for minor lining wear and should be utilized as such. If brake pedal travel is excessive, drums must be removed and lining wear limits inspected.

Disc Brakes - No adjustment required.

Drum Brakes - Brakes have on common adjuster to control both shoes; it is located on rear of backing plate. To adjust, raise vehicle and turn adjuster clockwise until drum locks; back off adjuster until drum is just free to turn.

Hand Brake - If hand brake is disfunctional because of inability to lock drums, ratchet travel generally needs adjusting. NOTE - Before attempting to reduce lever travel, adjust drum brakes. Raise vehicle until both rear wheels clear ground. Set hand brake in fully relaxed position; ensure both drums rotate. Apply hand brake three ratchet serrations. Adjust nuts on hand brake lever until heave hand pressure will just turn drum (tire and wheel). Release hand brake and ensure both drums rotate freely. NOTE - It is imperative that both drums offer equal resistance if maximum braking is to be achieved.

BLEEDING SYSTEM

BRAKE FLUID LEVEL CAUTION - If master cylinder has been allowed to run dry it will be necessary to bleed hydraulic system in addition to refilling master cylinder.

HYDRAULIC SYSTEM LEAK NOTE - If a leak is diagnosed in hydraulic system it will be necessary to bleed entire system after repairing deficiency.

Fill master cylinder reservoir to correct level and maintain level throughout operation. Attach tube to front and rear bleed screws on left side of vehicle. Submerge free ends into half-full container of brake fluid. Open bleed screw on-half turn, fully depress brake pedal, and close screw before allowing pedal to return to relaxed position. Repeat operation until Air bubbles cease to appear. Move tubes to right side of vehicle and continue bleeding procedures.

REMOVAL AND INSTALLATION

LINING REPLACEMENT (DISC BRAKES)

DRUM BRAKE ASSEMBLY

Removal - Raise vehicle and remove tire and wheel.Depress retaining spring and extract keeper pins. Remove retaining spring and using suitable pliers withdraw friction pads.

Installation - Clean exposed surface of piston and caliper cavity. Seat piston in bore, fit new friction pad assemblies to caliper, ensuring piston operated pad has free movement. Install retaining spring and insert keeper pins. Loosen screw on caliper top adjacent to pivot pin boss and press pedal several times to centralize brake rotor and pads.

LINING REPLACEMENT (DRUM BRAKES)

Removal - Raise rear of vehicle, remove tire and wheel and fully release hand brake. Remove hub cap and nut, using suitable tools (18G-304 & 18G-304-B). Withdraw brake drum and hub unit. Disengage mounting springs, return springs and hand brake lever. Separate brake shoes from wheel cylinder and brake adjuster while removing from backing plate.

Installation - To install brake drum lining, reverse removal procedures noting the following: ensure mounting springs are located in proper brake shoe holes.

BRAKE CALIPER 

Removal - Remove friction pad assemblies as previously outlined. Disconnect hydraulic inlet line. Remove two bolts securing caliper to front hub and withdraw caliper from disc and hub assembly.

Installation - To install sliding caliper, reverse removal procedures and bleed hydraulic system.

BRAKE ROTOR (DISC)

BRAKE ROTOR NOTE - Rotor and hub are separate assemblies that, once off vehicle, can be disassembled.

Removal (All Models) - Raise vehicle and suitably support font end. Remove brake caliper assembly as previously described.Extract cotter key, mounting nut, washer, and outer bearing. Pull hub assembly from mounting position with inner bearing and grease seal intact. If necessary, rotor can now be disassembled from hub.

Installation - To install brake hub assembly, reverse removal procedures noting the following: It is advisable to replace inner wheel bearing grease seal. Tighten wheel bearing to specifications. See Wheel Bearing Adjustment in WHEEL ALIGNMENT Section.

BRAKE DRUM

Removal (Rear Drum) - Raise vehicle and block front wheel. Remove tire and wheel. Set hand brake in fully released position. Using suitable tools (18G-304 & 18G-304-B), withdraw brake drum and hub assembly.

Installation - To install brake drum, reverse removal procedure noting the following: brake shoes may need to be loosened to install drum.

MASTER CYLINDER

Removal - Disconnect hydraulic lines from master cylinder and plug open ends. Withdraw two nuts securing master cylinder to fire wall and lift off, leaving the push rod attached to brake pedal.

INERTIA VALVE

Installation - To install master cylinder, reverse removal procedures noting the following: Check clearance between pedal back and stop (.030"). It may be necessary to readjust position of stop light switch. Refill master cylinder and bleed entire hydraulic system.

VACUUM SERVO UNIT

Removal - Disconnect both unions from slave cylinder and release vacuum line form check valve located in

in servo housing. Withdraw the top mounting nuts from servo housing and loosen clamp from neck of slave cylinder. Lift off servo unit noting the holes in mounting brackets are slotted for easy installation.

Installation - To install vacuum servo unit, reverse removal procedures noting the following: bleed hydraulic system.

INERTIA VALVE

Removal - Valve can be removed by disconnecting and plugging all hydraulic lines. Remove two mounting bolts and lift valve assembly from under right hand sub-frame crossmember.

MASTER CYLINDER ASSEMBLY
(TANDEM PISTON)

Installation - To install inertia valve, reverse removal procedures noting the following: Valve must be installed with "FRONT" marking facing correctly.

OVERHAUL

BRAKE CALIPER

Disassembly - With friction pads and brake caliper removed as previously described, clean all dirt from caliper cavity. Reconnect brake hose and support caliper. Push pedal down gently until piston can be removed by hand. Using suitable blunt nose tool, carefully remove fluid seal from groove. Remove dust seal by inserting a screwdriver between retainer and seal and gently force retainer from bore.

Reassembly - Coat new fluid seal with brake fluid and ease seal, with fingers, into groove. Loosen bleed screw one turn and fit piston with cut-away facing upward. Seat piston until new seal into retainer and retainer to piston. Seat piston using suitable tool (18G-590). After reassembly and installation has been completed, bleed hydraulic system and refill master cylinder.

MASTER CYLINDER

SLIDING BRAKE CALIPER

Disassembly - Begin by compressing return spring and disengaging Spirolox ring. Using suitable tool (18G-1112) remove piston retaining circlip. Move piston in bore until nylon bearing and cap seal are free. Withdraw plain washer and using suitable tool (18G-1112) remove inner circlip. Extract primary and secondary piston assemblies with stop washer. Compress spring separating two pistons and drive out roll pin retaining piston link. Disassemble all rubber components and replace. Separate reservoir and replace seals. After removing and inspecting connector unions, fit copper gaskets.

Reassembly - With components on bench locate piston on secondary piston head, convex side first. Carefully fit secondary cup, lip last, over piston end. Carry out all remaining procedures in reverse removal procedures. After reinstallation, bleed hydraulic system.

Audi 100LS 1977 Brake Repair Guide

DESCRIPTION

Brake system is hydraulically operated, utilizing a tandem master cylinder and power brake unit. Front disc brakes consist of rotors attached to wheel hub and drive shaft and two piston calipers attached to strut assembly. Disc pads are equipped with a ceramic transmitter-type wear sensor. Transmitter is mounted on cross spring and will break when contact is made with pad plates, interrupting control circuit and causing indicator light on instrument panel to be activated. All models are equipped with pressure regulator that is mounted to body and operated by a spring connected to rear axle. Rear brakes are leading-trailing shoe/drum type, using a dual piston wheel cylinder. Parking brake is cable actuated, operating secondary shoes of rear brake assemblies.

ADJUSTMENT

NOTE - Adjustments or readjustments should be carried out on cold brakes. However, brakes must be warm when testing. Instrument panel trim must be removed to adjust master cylinder push rod free play.

MASTER CYLINDER PUSH ROD FREE PLAY

Adjustment of piston rod play at master cylinder is made by loosening lock nut and turning piston rod until correct free play, measured at brake pedal, is obtained. When correct free play of .039" is obtained between push rod and piston, free play is measured at brake pedal will be approximately .2".

FRONT DISC BRAKES

Front disc brakes are self-adjusting, therefore, no adjustment in service is required.

REAR DRUM BRAKES

Raise and support rear of vehicle and release parking brake. Using a 17 mm wrench, tighten eccentric adjusters until wheels can no longer be turned by hand. Loosen eccentric adjusters until wheels are just fee to turn.

PARKING BRAKE

NOTE - Because of the residual pressure in brake regulator, the right rear brake shoes might not fully release from drum. Before adjustment, move lever on pressure regulator rearward.

Raise and support rear of vehicle and adjust rear brakes. Lift parking brake lever until it engages third ratchet stop. Adjust nut at equalizer until rear wheels are just free to turn. When parking brake lever is pulled up one additional notch (to fourth ratchet stop), rear wheels should be locked.

BRAKE PRESSURE REGULATOR

Fig. 1 Brake Pressure Regulator Adjustment Points

Checking & Adjusting - 1) Rock vehicle back and forth several times, then measure distance from top of rim to bottom of fender lip. Measurement must be made with trunk empty, gas tank full, and driver in vehicle

2) Raise vehicle on a hoist and make measurement again. If there is a difference in measurements, adjust by turning clamps. See Fig. 1.

3) Connect pressure gauges to left front and right rear wheels. Bleed pressure gauges. Apply pressure to foot pedal and note reading at gauge. Repeat procedure on right and left rear wheels.

                        Brake Pressure Values

Application                                    Pressure (psi)

Left Front.............................................  700

Right Rear............................................. 475-625

Right Front............................................ 1400

Left Rear............................................... 765-945

NOTE - DO NOT adjust brake pressure regulator when pressure is applied to brake pedal.

4) If pressure at rear wheels is to high, release spring and move spring support arm forward. If pressure at rear wheels is too low, move support arm rearward.

HYDRAULIC SYSTEM BLEEDING

Fill master cylinder reservoir with brake fluid and maintain level throughout bleeding operation. Attach a hose to bleeder screw, and immerse opposite end in a container partially full of brake fluid. Open bleeder screw, approximately one-half turn, depress brake pedal, close bleeder screw, and slowly return pedal. Continue operation until air bubbles are no longer seen in discharged fluid. Bleeding sequence is left-rear, right-rear, right-front, left-front.

REMOVAL & INSTALLATION

FRONT DISC BRAKE PADS

Removal - Remove lock clips. Pull out retaining pins so they project into openings in side members. NOTE - Do not remove rubber grammets from side member holes. Using a suitable extractor tool (SB-3), remove disc pads from caliper.

NOTE - Disc pads can be removed on right side only after removing front exhaust pipe.

Installation - Press both pistons into caliper bores.

NOTE - Fluid level in master cylinder reservoir will rise. Siphon sufficient fluid to prevent reservoir from overflowing. Ensure pistons are in correct alignment in bores using suitable tool (B-5). Install disc pads in recesses of caliper, slide in retaining pins, and install lock clip. Pump brake pedal several times to position disc pads. Bleed hydraulic system if necessary.

Fig. 2 Audi 100LS Rear Brake Assembly

FRONT DISC BRAKE CALIPER

Removal - With wheel and tire removed, take out disc pads. Disconnect hydraulic line from caliper. Remove bolts securing caliper and take off caliper.

Installation - To install brake caliper, reverse removal procedure and bleed hydraulic system

FRONT DISC BRAKE ROTOR

Removal - With wheel and tire assembly removed, take off caliper. Do not disconnect hydraulic line unless necessary. Remove screw retaining rotor to wheel hub (if equipped) and withdraw rotor.

Installation - To install rotor assembly, reverse removal procedure and bleed hydraulic system.

REAR BRAKE DRUM

Removal - Raise and support vehicle, remove wheel and tire assembly. Pry off dust cap, remove cotter pin from hex nut, and remove nut. Remove brake drum making sure that retaining washer and wheel bearing do not fall out.

Installation - To install, reverse removal procedure, adjust brakes, and adjust wheel bearings. See Wheel Bearing Adjustment in WHEEL ALIGNMENT Section.

REAR BRAKE SHOES

Removal - With brake drum removed, remove retaining spring for brake shoes. Remove shoes as an assembly by disconnecting spring at bottom, pulling shoes back from wheel cylinder, and disconnecting parking brake cable.

Installation - To install, reverse removal procedure and note the following: Make sure long ends of retaining clip and spring are installed on secondary shoe and parking brake lever. Ensure brake shoes are correctly  positioned on wheel cylinder pistons.

REAR BRAKE WHEEL CYLINDER

Removal - With drum and shoes removed, depress pedal approximately 1.2" and hold in position using a suitable pedal support. Disconnect hydraulic line from rear of backing plate and plug line to prevent loss of fluid. Remove retaining screws and wheel cylinder.

Installation - To install, reverse removal procedure, adjust brakes and bleed hydraulic system.

MASTER CYLINDER

Removal - Disconnect hydraulic line at rear of master cylinder. Depress brake pedal 1.2-1.6" and hold in position using a suitable pedal support. Disconnect remaining hydraulic line and cylinder mounting nuts. Separate master cylinder from power unit taking care not to lose "O" ring installed betweend them.

Installation - To install, reverse removal procedure and bleed hydraulic system.

POWER BRAKE UNIT

Removal - Siphon brake fluid from master cylinder reservoir and disconnect hydraulic lines. Loosen hose clamp and disconnect vacuum hose from power unit. From inside vehicle remove trim below instrument panel as necessary. Disconnect push rod from brake pedal, remove power unit adapter attaching nuts, and remove power unit and master cylinder from engine compartment as an assembly. Separate master cylinder and adapter from power unit.

Installation - To install, reverse removal procedure and note the following: Be sure to install "O" ring between master cylinder and power unit. Install adaptor to power unit so that center punch mark on adaptor is located on lower right side facing engine. To complete installation, adjust pedal push rod free play and bleed hydraulic system.

Check Valve Replacement - A vacuum check valve is located in vacuum line between intake manifold and power unit. To remove, loosen hose clamps, separate vacuum hoses from check valve, and remove check valve. To install, reverse removal procedure and note the following: Check valve stamped with the word "MOTOR" and a arrow. End of  valve in which arrow points must be connected to shorter hose from intake manifold.

OVERHAUL

FRONT DISC BRAKE CALIPER

Fig. 3 Front Disc Brake Caliper Assembly

Disassembly - Remove disc pads. Pry out retaining ring and remove dust seal by hand. Place a small block of wood in caliper cavity, and remove piston by applying compressed air to fluid inlet. Remove remaining piston in same manner. Remove seal from caliper bore using a piece of wood or plastic. NOTE - Do not use hard or sharp tools for this purpose. Do not separate caliper halves.
Cleaning & Inspection - Clean all parts in alcohol only. Check cylinder bore and piston
 for damage. NOTE -  Do not machine caliper bore or piston. Parts are serviced by replacement only.

Fig. 4 Using a 20° Gauge to Position Caliper Piston

Reassembly - Coat all parts with ATE brake cylinder paste (or equivalent), reverse disassembly procedure, and note the following. Use new seals, dust boots, and retaining rings when reassembling. When installing piston, make sure machined surface of piston face makes a 20 degree angle to wall of caliper bore (see illustration). Install disc pads after caliper has been installed on vehicle.
REAR WHEEL CYLINDER
Disassembly - Thoroughly clean outside of cylinder. Remove end caps, piston and seal assemblies, and spring. Remove dust cap and bleeder screw.
Cleaning & Inspection - Clean all parts in alcohol only. Check all parts for rust, corrosion, or other damage. Check cylinder bore and piston for wear. Maximum allowable cylinder diameter is .6287; minimum allowable piston diameter .6197". Manufacturer recommends replacing rubber components each time cylinder is disassembled.

Reassembly - Reverse disassembly procedure and not the following: Apply a thin coat of ATE brake cylinder paste (or equivalent) to all parts during assembly.
MASTER CYLINDER
Disassembly - Thoroughly clean outside of master cylinder. Remove hydraulic fluid reservoir, remove retaining ring, and remove primary piston assembly. Loosen or remove (if necessary) piston stop screw and remove secondary piston assembly. Disassemble primary and secondary piston assemblies.
Cleaning & Inspection - Clean all parts in alcohol only. Dry all parts with compressed air and check that compensating parts of cylinder are free of obstructions. Check cylinder bore and pistons for rust, corrosion or other damage. Inspect cylinder bore and pinion for wear. Maximum allowable cylinder diameter is .817:; minimum allowable piston diameter is .807". Manufacturer recommends replacing all rubber parts whenever cylinder has been disassembled.
Reassembly - Reverse disassembly procedure and note the following: Do not apply grease to push rod as damage may result to rubber components.
POWER BRAKE UNIT
NOTE - Manufacturer does not recommend overhaul of power brake unit.

Fig. 5 Sectional View of Audi 100LS Tandem Master Cylinder

Audi S90 & 100 1970-73 Brake Repair Guide

Models Covered

• S90 (1970-72)
• 100 (1970-73)

DESCRIPTION

Brake system is hydraulically operated, utilizing a tandem master cylinder and Teves T 51/349 power brake unit. Front disc brakes consist of rotors attached to transmission output flanges, and two-piston calipers attached to transmission. Disc pads are equipped with a ceramic transmitter-type wear sensor. Transmitter is mounted on cross spring and will break when contact is made with pad plates, interrupting control circuit and causing indicator light on instrument panel to be activate. Rear brakes are leading-trailing shoe/drum type, using a dual piston wheel cylinder. Parking brake is cable actuated, operating secondary shoes of rear brake assemblies.

ADJUSTMENT

NOTE - Adjustments or readjustments should be carrier out on cold brakes. However, brakes must be warm when testing. Instrument panel trim must be removed to adjust master cylinder push rod free play.

MASTER CYLINDER PUSH ROD FREE PLAY

Check brake pedal free play by measuring distance between master cylinder push rod and master cylinder piston. This measurement should be .039" (1.0 mm), which would give free play of .20" (5.08 mm) at brake pedal. If necessary to adjust, loosen lock nut on push rod and turn push rod until correct clearance is obtained. Tighten lock nut and again measure pedal free play at brake pedal.

FRONT DISC BRAKES

Front disc brakes are self-adjusting, therefore, no adjustment in service is required.

REAR DRUM BRAKES

Raise and support rear of vehicle release parking brake. Using a 17 mm wrench, tighten eccentric adjusters until wheels can no longer be turned by hand. Loosen eccentric adjusters until wheels are just free to turn.

PARKING BRAKE

Raise and support rear of vehicle and adjust rear brakes. Lift parking brake lever until it engages third ratchet stop. Adjust nut at equalizer until rear wheels are just free to turn. When parking brake lever is pulled up one additional notch (to fourth ratchet stop), rear wheels should be locked.

HYDRAULIC SYSTEM BLEEDING

Fill master cylinder reservoir with brake fluid and maintain level throughout bleeding operation. Attach a hose to bleeder screw, and immerse opposite end in a container partially full of brake fluid. Open bleeder screw approximately one-half turn, depress brake pedal, close bleeder screw, and slowly return pedal. Continu operation until air bubbles are no longer seen in discharge fluid. Bleeding sequence is left-rear, right-rear, right-front, left-front.

REMOVAL & INSTALLATION

FRONT DISC BRAKE PADS

Removal - Remove lock clips. Pull out retaining pins so they project into openings in side members. NOTE - Do not remove rubber grommets from side member holes. Using a suitable extractor tool (SB-3), remove disc pads from caliper.

NOTE - Disc pads can be removed on right side only after removing front exhaust pipe.

Installation - Press both pistons into caliper bores.

NOTE - Fluid level in master cylinder reservoir will rise.

Siphon sufficient fluid to prevent reservoir from overflowing. Ensure pistons are in correct alignment in bores using suitable tool (B-5). Install disc pads in recesses of caliper, slide in retaining pins, and install lock clip. Pump brake pedal several times to position disc pads. Bleed hydraulic system if necessary.

FRONT DISC BRAKE CALIPER & ROTOR

Removal - 1) On vehicles equipped with automatic transmission, disconnect steering damper from its bracket and move out of way. On all models, depress brake pedal approximately 1.2" (30.48 mm) and hold in this position by using suitable pedal support. Disconnect temperature transmitter wire from connector (near transmission)

2) On automatic transmission equipped vehicles, disconnect hydraulic line at union on transmission, EGR line at exhaust pipe, and exhaust pipe from hangers. On all models, disconnect and remove front exhaust pipe and shield from manifold, and drive shaft at stub axle.

3) Remove ball joint mounting bolts, pull wheel downward, and swing out steering knuckle after prying it off ball joint. Remove disc brake pads, leaving spring and wire in vehicle. Remove EGR filter from oil  pan. Remove caliper mounting nuts, then remove caliper and rotor from stub axle. NOTE - If necessary, pry engine assembly to one side to ease removal.

Installation - To install, reverse removal procedure, tighten caliper mounting bolts securely, and bleed hydraulic system.

REAR BRAKE DRUM

REAR BRAKE ASSEMBLY

Removal - Raise and support vehicle, remove wheel and tire assembly. Pry off dust cap, remove cotter pin from hex nut, and remove nut. Remove brake drum making sure that retaining washer and wheel bearing do not fall out.

Installation - To install, reverse removal procedure adjust brakes, and adjust wheel bearings. See Wheel Bearing Adjustment in WHEEL ALIGNMENT Section.

REAR BRAKE SHOES

Removal - With brake drum removed, remove retaining spring for brake shoes. Remove shoes as an assembly by disconnecting spring at bottom, pulling shoes back from wheel cylinder, and disconnecting parking brake cable.

Installation - To install, reverse removal procedure and not the following: Make sure long ends of retainin clip and spring are installed on secondary shoe and parking brake lever. Ensure brake shoes are correctly positioned on wheel cylinder pistons.

REAR BRAKE WHEEL CYLINDER

Removal - With drum and shoes removed, depress brake pedal approximately 1.4" (35.56 mm) and hold in this position by using suitable pedal support. Disconnect remaining hydraulic line and cylinder mounting nuts. Separate master cylinder from power unit, taking care not to lose "O" ring installed between units.

Installation - To install, reverse removal procedure, adjust brakes and bleed hydraulic system.

MASTER CYLINDER

Removal - Disconnect hydraulic line at rear of master cylinder. Depress brake pedal 1.2-1.6" and hold in position using a suitable pedal support. Disconnect remaining hydraulic line and cylinder mounting nuts. Separate master cylinder from power unit taking care not to lose "O" ring installed between them.

Installation - To install, reverse removal procedure and bleed hydraulic system.

POWER BRAKE UNIT

Removal - Siphon brake fluid from master cylinder reservoir and disconnect hydraulic lines. Loosen hose clamp and disconnect vacuum hose from power unit. From inside vehicle, remove trim below instrument panel as necessary. Disconnect push rod form brake pedal, remove power unit adapter attaching nuts, and remove power unit and master cylinder from engine compartment as an assembly. Separate master cylinder and adaptor from power unit.

Installation - To install, reverse removal procedure and note the following: Be sure to install "O" ring between master cylinder and power unit. Install adaptor to power unit so that center punch mark on adaptor is located on lower right hand side facing engine. To complete installation, adjust pedal push rod free play and bleed hydraulic system.

Check Valve Replacement - A vacuum check valve is locate in vacuum line between intake manifold and power it. To remove, loosen hose clamps, separate vacuum hoses from check valve, and remove check valve. To install, reverse removal procedure and not the following: Check valve is stamped with the word "MOTOR" and an arrow. End of valve in which arrow points must be connect to shorter hose from intake manifold.

OVERHAUL

FRONT DISC BRAKE CALIPER

FRONT DISC BRAKE CALIPER ASSEMBLY

Disassembly - Remove disc pads. Pry out retaining ring and remove dust seal by hand. Place a small block of wood in caliper cavity, and remove piston by applying compressed air to fluid inlet. Remove remaining piston in same manner. Remove seal from caliper bore using a piece of wood or plastic. NOTE - Do not use hard or sharp tools for this purpose. Do not separate caliper halves.

FRONT DISC BRAKE CALIPER ASSEMBLY

Cleaning & Inspection - Clean all parts in alcohol only. Check cylinder bore and piston for damage. NOTE - Do not machine caliper bore or piston. Parts are serviced by replacement only.

PINION INSTALLATION

Reassembly - Coat all parts with ATE brake cylinder paste (or equivalent), reverse  disassembly procedure, and note the following: Use new seals, dust boots, and retaining rings when reassembling. When installing piston, make sure machined surface of piston face makes a 20° angle to wall of caliper bore (see illustration). Install disc pads after caliper has been installed on vehicle.

REAR WHEEL CYLINDER

Disassembly - Thoroughly clean outside of cylinder. Remove end caps, piston and seal assemblies, and spring. Remove dust cap and bleeder screw.

AUDI MASTER CYLINDER
(COMPONENT PARTS)

Cleaning & Inspection - Clean all parts in alcohol only. Check all parts for rust, corrosion, and damage. Check cylinder bore and piston for wear or damage. Cylinder bore should not exceed .6287" (16.00 mm) and piston diameter should not be less than .619" (15.74 mm). NOTE - Manufacturer recommends replacing rubber components on each disassembly.

Reassembly - Reverse disassembly procedure and not the following: Apply a thin coat of ATE brake cylinder paste (or equivalent) to all parts during assembly.

MASTER CYLINDER

Disassembly - Remove reservoir, brake light switch, circlip and dismantle cylinder. To extract piston, unscrew stop screw.

Cleaning & Inspecting - Clean all parts in denatured alcohol. Inspect bore and piston for rust or wear and replace any parts out of tolerance. It is advisable to always replace rubber parts.

Reassembly - Preassemble pistons and coat cups with ATE brake cylinder paste (or equivalent). Insert assembly into cylinder bore, install stop screw and circlip. Install brake light switch and resrevoir.

NOTE - Models without power brake servo differ slightly. Primary piston desgin is somewhat varied. Piston is equipped with only on secondary boot. There is no air compensating bore. Brake light switch location is different.