Sunday, March 31, 2013

Dodge Colt 1971-43 Brake Repair Guide

DESCRIPTION
Dodge Colt uses two different braking systems on 1973 models. Early models (manufactured through December, 1972) use dual piston fixed caliper disc brakes on front wheels, and manually adjusted leading-trailing shoe/drum brakes on rear wheels. Late models (manufactured since January, 1973) use single piston floating caliper disc brakes on front wheels, and self-adjusting leading-trailing shoe/drum brakes on rear wheels. Models equipped with the later model braking system with the following identification numbers.
6H23K35 117753                                          6L21K35 307874
6H23K39 124991                                          6L21K39 300111
6H41K35 108843                                          6P23K35 000643
6H41K39 114906                                          6P23K39 000457
6H45K35 109389                                          6P45K35 000411
6H45K39 116220                                          6P45K39 000521
All models are equipped with tandem master cylinder, consisting of independent front and rear hydraulic systems; a pressure differential warning switch, actuating on indicator lamp on instrument panel in the event of a pressure drop in front or rear hydraulic system; and a cable actuated parking brake assembly, acting on rear wheels.
ADJUSTMENT
FRONT DISC BRAKE PADS
Front disc brakes are self-adjusting, therefore, no adjustment in service is required.
REAR BRAKE SHOES
Early Models - Release parking brake. Using a suitable brake adjusting tool (CT-1107), tighten adjuster clockwise until brake shoes just contact drum. Back off adjuster until drum rotates freely. When propery adjusted, brake shoe-to-drum clearance should be .004-.012"
Late Models - Rear drum brakes are self-adjusting, therefore, no adjustment in service is required.
PARKING BRAKE
All Models - 1) Release parking brake lever. Loosen cable lever attaching bolt and adjusting nut, and move cable lever to right. Adjust clearance to left cable to .04", then tighten attaching bolt. Clearance is measured between extension lever and backing plate on early models, or between extension lever and stopper on late models.
2) With let cable adjusted, turn adjusting nut until some clearance is obtained at right extension lever. With parking brake properly adjusted, parking brake lever stroke should be less than 7 notches (14 clicks) on early models, or 4-6 notches (8-12 clicks) on late models.
HYDRAULIC SYSTEM BLEEDING
Attach a bleed tube to wheel cylinder bleeder screw and immerse opposite end of tube in container partially filled with brake fluid. Depress and release pedal several times, hold in applied position, loosen bleeder screw, allow air to escape and tighten bleeder screw. Continue operation until air bubbles are no longer seen in discharged fluid. Repeat procedure at remaining brake lines until all air is bled from system. Bleeding sequence is right-rear, left-rear, left-front, and right-front.
REMOVAL & INSTALLATION
CROSS SPRING INSTALLATION
FRONT DISC BRAKE PADS
Removal (Early Models) - Raise and support vehicle and remove front wheel. Remove clips holding pad retaining pins in place, then remove pins and cross spring. Using pliers, pull disc pads from caliper assembly.
Installation - Press pistons to bottoms of bores using a suitable tool, and install disc pads and shims. NOTE -  Make sure shims are installed between pad and piston, and arrow mark on shim faces forward. Insert upper pin into caliper with "A" portion of cross spring hooked on retaining pin, then install clip. Insert lower retaining pin and install clip, making sure pad shim is between cross spring flanges ("B"). Firmly press "C" portion of spring onto retaining pin. See Illustration.
Removal (Late Models) - Raise and support vehicle and remove front wheel. Remove pad protector by prying up edge of clip at center of protector with a screwdriver. Hold center of "M" clip, detach "M" clip
SPRING & CUP INSTALLATION
from pad and its ends from retaining pins from caliper and remove "K" spring. Remove pads from caliper by grasping backing plate area of pads with pliers.
Installation - Press piston to bottom of bore using a suitable tool, install disc pads and retaining pins. Install "K" spring and "M" clip, making sure positions are not reversed.
See illustration. Install pad protector, making sure clips face outward.
FRONT DISC BRAKE CALIPER
Removal (All) - With disc pads removed, disconnect hydraulic line and remove bolts attaching caliper assembly to steering knuckle, and remove caliper assembly.
Installation - Reverse removal procedure, tighten caliper mounting bolts evenly, and bleed hydraulic system.
FRONT DISC BRAKE ROTOR
BRAKE SHOE INSTALLATION
(EARLY MODELS)
Removal (All) - With caliper assembly removed, remove hub dust cap, cotter pin, lock nut, and adjustment nut. Pull hub and rotor assembly from spindle, taking care not to drop outer wheel bearing. Remove bolts attaching rotor to hub, then separate.
Installation - Reverse removal procedure, tighten rotor-to-hub bolts evenly, and adjust wheel bearings. 
REAR BRAKE SHOES
Removal (Early Models) - Raise and support vehicle and remove brake drum. Remove shoe hold-down springs and shoe return spring. Pull upper shoe ends from wheel cylinder and remove brake shoe assembly.
Installation - Reverse removal procedure and note the following: Apply brake grease to all shoe contact points of backing plate, adjuster assembly, and wheel cylinder. Brake shoes are not interchangeable. See illustration for proper installation.
FRONT DISC BRAKE ASSEMBLY (EARLY MODELS)

REAR BRAKE ASSEMBLY (LATE MODELS)
Removal (Late Models) - Raise and support vehicle and remove brake drum. Remove shoe hold-down springs. Disconnect strut-to-shoe spring and upper shoe return spring end from trailing shoe. Remove trailing shoe and lower return spring. Hold adjusting latch downward, pull adjusting lever toward center of brake, and remove leading shoe assembly. Remove upper shoe return spring and strut-to-shoe spring.
Installation - Reverse removal procedure and note the following: Apply brake grease to all shoe contact points of backing plate, adjuster assembly, and wheel cylinder. Adjust amount of engagement of adjusting lever with strut only after pulling lever fully toward center of brake. Note the adjusting lever and latch spring differ between right and left sides.
REAR WHEEL CYLINDER
Removal (All) - With rear drum and brake shoes removed, disconnect hydraulic line from wheel cylinder at rear of backing plate, remove volts attaching cylinder, and remove wheel cylinder.
Installation - Reverse removal procedure, tighten mounting bolts evenly, and bleed hydraulic system.
MASTER CYLINDER
Removal - Disconnect hydraulic lines from master cylinder, then depress pedal slowly several times to discharge fluid. Remove clevis bolt retaining master cylinder push rod to pedal, remove cylinder mounting bolts, and remove master cylinder.
Installation - Reverse removal procedure, check and adjust pedal height, and bleed hydraulic system.
OVERHAUL
FRONT DISC BRAKE ASSEMBLY
(LATE MODELS)
FRONT DISC BRAKE CALIPER 
Disassembly (Early Models) - Remove retaining rings and  dust seals. Remove outer piston from caliper by holding inner piston with a screw driver, and applying compressed air to fluid inlet. Remove inner piston by inserting a driver in fluid inlet and tapping out. Remove piston seals, taking care not to damage caliper bores or seal grooves. NOTE - Do not separate caliper halves or loosen bridge bolts.
Cleaning & Inspection - Clean all parts in brake fluid and inspect for wear or damage; replace all worn, damaged or rusty cylinders and pistons. NOTE -  Manufacturer recommends replacing piston seals and dust seals whenever caliper has been disassembled.
Reassembly - Apply rubber grease to piston seals and install into caliper bores. Lubricate cylinder walls and pistons with rust preventative oil, and install pistons, taking care not to twist piston when installing. Install dust seals and retaining rings, lubricating inner side of dust seals with rubber grease before installation.
Disassembly (Late Models) - Remove caliepr attaching bridge bolts and separate outer and inner caliper halves. Remove retaining ring and dust seal, apply compressed air to fluid inlet, and remove piston. Remove piston seal taking care not to damage caliper bore or seal groove.
Cleaning & Inspection - Clean all metal parts in trichlorroethylene, alcohol, or brake fluid; clean piston seal in brake fluid  or alcohol; clean dust seal and other rubber parts in alcohol only. Inspect caliper bore and piston for wear, damage, or rust; replace parts as necessary. NOTE - Manufacturer recommends replacing piston seal and dust seal whenever piston has been removed.
Reassembly - Reverse disassembly procedure and note the following: Apply rubber grease to piston seal and brake fluid to piston when reassembling. If torque plate was remove from inner caliper half, clean torque plate shaft and shaft bore in caliper, then apply special rubber grease to rubber bushing, wiper seal inner surface, and torque plate shaft before reassembly. Tighten bridge bolts of caliper halves evenly.
MASTER CYLINDER
Disassembly - Removedust boot, retaining ring, stop washer, and piston stop bolt, and withdraw primaryNOTE - Do not disassemble primary piston assembly. Remove check valve caps, tube seats, check valves, and check valve spring.
piston assembly, secondary piston assembly, and secondary return spring from master cylinder.
Inspection - Check master cylinder bore and piston for wear or other damage and replace as necessary. Check clearance between cylinder bore and piston; if clearance exceeds .006", replace parts as necessary. Check all parts of secondary piston assembly; if any parts are found defective, replace complete secondary piston assembly.
Reassembly - Reverse disassembly procedure and note the following: Apply rubber grease to all parts (except boots) before reassembly. When assembled, check that return port is not block by piston cup when piston is located at return position.




Capri 1973-77 All Models Brake Repair Guide

DESCRIPTION
The brake system is hydraulically operated, utilizing a tandem master cylinder and a power brake unit. Front disc brakes consists of rotors attached to wheel hubs, a dual piston floating caliper assemblies. Rear brakes are leading-trailing shoe/drum type, using dual piston wheel cylinders. A combination valve is used to distribute correct pressure to each rear brake wheel cylinder. Parking brake system is cable and rod operated acting on rear brake assemblies.

ADJUSTMENT
FRONT DISC BRAKE PADS
Front disc brakes are self-adjusting; therefore, no adjustment in service is required.
REAR BRAKE SHOES
Rear drum brakes are self-adjusting (actuated by parking brake linkage); therefore, no adjustment in service is required.
PARKING BRAKE LINKAGE
NOTE - It should only be necessary to adjust parking brake system in the event of wear on linkage components or replacement of parts. DO NOT adjust for rear brake wear.
Ensure parking brake is fully released, then raise and support vehicle. To adjust primary cable, engage keyed sleeve (A) into abutment slot (B), then turn adjuster nut (C) until all slack is removed from cable. Parking brake is properly adjusted when clearance between parking brake lever stop and brake backing plate is .039 - .059" (1.0-1.5mm).
COMBINATION VALVE
Warning Light Test - 1) Turn ignition switch to on position and set parking brake, warning light should be on. If there is no light, electrical problem is indicated.
2) Release parking brake and operate pedal a few times; light should not work. If light comes on, hydraulic problem is indicated.
NOTE - Piston in combination valve is self-centering.
BLEEDING HYDRAULIC SYSTEM
1) Fill master cylinder reservoir with brake fluid and maintain level throughout bleeding operation. NOTE -
Fig. 1 Parking Brake Adjustment Points
Piston in combination valve is self-centering and does not need to be held in central position while brakes are being bled. Attach a hose to right front brake bleeder screw and immerse opposite end in container partially full of brake fluid.
2) Open bleeder screw approximately one-half turn, depress brake pedal fully, then allow it to return to its off position. Continue depressing brake pedal, pausing after each return stroke to allow full recuperation of master cylinder until fluid entering container is clean and free from air bubbles. Press brake pedal to the floor and hold it there while bleeder screw is tightened. Repeat operation on remaining brake in the following sequence: left front, left rear and right rear.
REMOVAL & INSTALLATION
FRONT DISC BRAKE PADS
Removal - Remove retaining pin clips and pins. Lift-out brake pads, tension springs and shim, (if equipped). NOTE - Clean any foreign matter from rotor. Ensure new pads are correct.
Fig. 2 Exploded View of Front Disc Brake Assy.
Installation - Press pistons to bottom of caliper bores. NOTE - Siphon sufficient fluid from master cylinder to prevent overflowing when pistons are pressed back into bores. Place tension springs on brake pads and shims, then install pads and shims into caliper assembly with arrow on shims pointing up. Install retaining pins and secure with pin clips. Pump brake pedal several times to position pads against rotor.
FRONT DISC BRAKE CALIPER
Removal - With caliper assembly removed, remove dust cap, cotter pin, adjusting nut, thrust washer, and outer bearing. Remove hub and rotor assembly, bend back lock tabs, remove attaching bolts, and separate rotor from hub. Discard lock tabs and bolts. 
Installation - Thoroughly clean mating surfaces of hub and rotor, position rotor on hub aligning mating marks, and install and tighten lock tabs and retaining bolts. To complete installation, reverse removal procedure, tighten all bolts evenly and adjust wheel bearings.
REAR BRAKE SHOES
Removal - Raise and support vehicle and remove rear wheels. Ensure parking brake is fully released, then
Fig. 3 Assembled View of Rear Drum Brake Components
remove brake drum. Remove brake shoe hold down spring and pins, then pull shoes from bottom guides and remove lower spring. Pull primary shoe from wheel cylinder  slot and self-adjuster arm, then undo spring and remove shoe. Unhook secondary shoe from parking brake lever, disconnect spring and remove shoe/
Installation - Hook spring and parking brake lever to secondary shoe. Connect upper spring to both shoes and position primary shoe over self-adjuster arm. Connect lower spring to shoes, then install lower end of shoes into guides. Install hold down springs and pins. Ensure brakes are centered and install brake drum.
REAR BRAKE WHEEL CYLINDER
Remova - Remove wheel, drum and brake shoe assemblies. Ensure there is no vacuum in booster system, then disconnect brake line from wheel cylinder. Remove wheel cylinder attaching bolts and lock washers and remove cylinder.
Installation - Place wheel cylinder into position, then connect brake line to cylinder and tighten fitting finger tight. Install and tighten cylinder attaching bolts with lock washers, then tighten brake line fitting. Install links in ends of cylinder then install shoe and adjuster assemblies. Install brake drum and bleed hydraulic system.
MASTER CYLINDER
Removal - Siphon fluid from reservoir, then disconnect hydraulic lines from master cylinder. Remove master cylinder to booster attaching nuts, then lift master cylinder from booster using care not to damage vauum seal.
Installation - Position master cylinder and fluid seal onto push rod and start all brake line union nuts. Connect master cylinder to booster and tighten attaching nuts. Tighten brake line union nuts and fill master cylinder with brake fluid. Bleed hydraulic system and check operation of brakes.
POWER BRAKE UNIT
Removal -  Disconnect power unit push rod from brake pedal. Remove nuts retaining master cylinder to power unit and position master cylinder out of way. Remove vacuum hose from power unit-to-firewall retaining screws, and remove power unit from vehicle. Remove retaining bracket and gasket from power unit.
Installation - Reverse removal procedure and note the following: Assemble retaining bracket to power unit using a new gasket. Make sure seal ring is installed on master cylinder between cylinder and power unit.
Fig. 4 Exploded View of Master Cylinder and Related Components

COMBINATION VALVE
FRONT DISC BRAKE CALIPER
Disassembly - Partially remove one piston from cylinder bore, remove snap ring, and remove sealng bellows from piston skirt. Remove piston by applying air pressure or hydraulic pressure to fluid inlet in caliper. Remove sealing bellows from annular ring in cylinder bore, and remove piston sealing ring. Repeat operation for remaining piston NOTE - DO NOT separate caliper halves.
Cleaning & Inspection - Clean pistons and cylinder bores in alcohol or brake fluid. CAUTION - DO NOT use mineral base solvents. Check all parts for wear, scoring or other damage; replace parts as necessary.
Reassembly - Install piston seal and sealing bellows into caliper bore. Lubricate piston with brake fluid and install through sealing bellows (crown first). Install inner edge of bellows in piston skirt, push piston to bottom
Fig. 5 Expanded View of Rear Wheel Cylinder Assy.
of cylinder, and install snap ring. Repeat operation for remaining piston.
REAR WHEEL CYLINDER
Disassembly - Remove dust boots and slide out piston assemblies. Remove seal from piston and spring from cylinder bore. Remove bleeder screw.
Cleaning & Inspection - Ensure pistons and cylinder are free of dirt, burrs and scratches. Thoroughly clean and dry all parts with a lint free cloth. Replace parts as necessary.
Reassembly - Install bleeder screw and tighten to specifications. Install new seals on pistons. Slide one piston into cylinder bore, then insert spring and remaining piston from opposite end and install dust boots.
MASTER CYLINDER
Disassembly - Remove reservoir from body. Loosen stop screw and push piston inward; remove snap ring. From primary chamber remove stop washer and primary piston assembly. With compressed air, force secondary piston assembly from its chamber.
Cleaning & Inspection - While apart clean master cylinder and inner components with alcohol. Thoroughly dry all parts before reassembly.
Reassembly - Install secondary piston and replacement parts together in secondary chamber. Press piston inward and install stop screw. Release piston and let it on contact stop screw. NOTE - Length of stop screw must not change with new seal. Reassemble primary piston and insert into chamber. Position stop screw. NOTE - Prevent burrs on secondary piston face by filling chambers with fluid before moving piston. Install reservoir.
COMBINATION VALVE
Disassembly - Unscrew and remove warning switch. Remove retaining bolt, then using a small screwdriver, gently push piston assembly out of valve bore. Remove two rubber seals from piston and slide of sleeves.
Cleaning & Inspection - Thoroughly clean all parts and dry with a lint free cloth. Inspect all parts for wear or damage and replace as necessary. Inspect retaining clips on piston for wear and tightness and replace if necessary.
Reassembly - Slide sleeves on piston and install new rubber seals. Slide piston assembly into cylinder, then install retaining bolt. Install warning switch.

Saturday, March 30, 2013

BMW General Hydraulic Brake Troubleshooting Guide 1973-75

HYDRAULIC BRAKE TROUBLE SHOOTING

BRAKE INSPECTION & TESTING
Inspect brakes at frequent intervals for pedal reserve (clearance between pedal and toeboard with pedal firmly depressed, while brakes are cold). Increase pedal reserve by adjusting brake shoe to drum clearance. Brakes should be tested on dry, clean reasonable smooth, level roadway (not and heavy pressure. CAUTION - Do not lock wheels and slide tires on raodway.

CONDITIONS AFFECTING BRAKE PERFORMANCE
Following external conditions may affect brake performance and should be corrected before proceeding with trouble shooting of brake mechanism;
Tires - Should be same size on each side of vehicle with approximately same tread design and inflation.
Loading - Wheels should be equally loaded, as heavily loaded wheels require more braking power.
Suspension - Faulty shock absorbers, incorrect front end alignment, or loose wheel bearings may give impression brake are too severe.

TROUBLE SHOOTING DRUM BRAKES
LOW PEDAL OR EXCESSIVE TRAVEL
Fluid low. Improper brake fluid. Air in system. Hoses expand under pressure. Wheel bearings or steering parts loose. Improper brake adjustment. Distorted shoes or linings. Master cylinder of power assist unit malfunction. Defective brake lines. Improper brake pedal free travel.
PEDAL APPLIED; NO BRAKING ACTION
Air in system. Leak past primary cup in master cylinder. Piston pushed back into bores. Hydraulic leak. Rear brakes out of adjustment.
ONE WHEELS DRAGS
Front wheel bearings loose. Shoes adjusted too tight. Shoe return spring broken or weak. Piston stuck or cups distorted. Clogged line or hose. Drum out-of-round. Loose anchor pin. Distorted shoe. Defective lining.
REAR BRAKES DRAG.
Improper adjustment. Parking cable frozen.
ALL WHEELS DRAG
Improper adjustment. Defective master cylinder. Improper adjustment of master cylinder push rod. Pedal linkage binding. Defective power unit.
VEHICLE PULLS TO ONE SIDE
Uneven tire treads. Worn front end parts. Incorrect front end alignment. Front wheel bearing loose. Loose steering. Loose backing plate or anchor pins. Loose or broken springs or "U" bolts. Improper lining. Improper adjustment. Defective drum. Loose or broken return spring. Defective wheel cylinder. Improper wheel cylinder size. Clogged or crimped line.
BRAKES SQUEAK OR NOISY
Improper lining. Lining loose on shoe. Foreign material on lining. Shoes scraping backing plate. Improper adjustment. Defective drum. Defective wheel cylinder. Weak or broken return springs. Loose anchor pin, wheel cylinder, or backing plate. Brake drum silencer spring missing (if equipped).
BRAKES FADE (FAIL TO HOLD)
Excessive heat build-up. Improper linings. Drums too thin. Lining soaked with fluid, or oil. Improper fluid.
PULSATING BRAKE PEDAL
Drums out-of-round. Loose brake drum. Worn or loose bearings. Bent rear axle.
HARD PEDAL
Grease or fluid on lining. Improper brake lining or fluid. Improper adjustment. Pedal linkage binding. Faulty master cylinder. Glazed linings. Defective brake drums.
BRAKES CHATTER
Improper shoe adjustment. Loose backing plate. Foreign material on lining.  Weak or broken return spring. Loose wheel bearings. Drum out-of-round. Distorted or misaligned shoes. Frozen strut rod bushings.
SNAPPING NOISE IN FRONT END.
Grooved backing plate pad. Lack of lubrication on moving parts. Loose drums or backing plate. Loose or worn front end parts. Defective lining.
POWER BRAKE UNIT DOES NOT BOOST
Test For Power Unit Operation - Stop engine and apply pedal pressure several times to remove all vacuum from system. Hold pressure on pedal and start engine. Pedal will move slightly forward when cylinder is operating.
Power Unit Does Not Operate - Vacuum check valve stuck closed. Vacuum pipe bent, broken or closed. Insufficient engine vacuum. Blocked air inlet. Air valve sticking in diaphragm. Faulty diaphragm. Faulty piston seal. Internal leaks.
Fig. 1 Sectional View of Typical Hydraulic Brake System


TROUBLE SHOOTING DISC BRAKES
LOW PEDAL OR EXCESSIVE TRAVEL
Fluid level low. Air in system. Defective brake lines. Defective caliper. Distorted pads or linings. Master cylinder or power assist unit malfunction. Misaligned piston and pad assembly. Low pedal after hard cornering or driving on rough road (pump pedal to correct). Disc runout excessive. Damaged caliper piston seal. Metering valve for front brakes not working Caliper seals soft or swollen. Improper brake pedal free travel.
HARD PEDAL
Master cylinder or power unit malfunction. Brake fluid, oil, or grease on linings. Lines or hoses kinked, dented, or collapsed. Cylinder cups swollen. Linings worn. Incorrect lining. Frozen or seized pistons. Metering valve or cylinder bores corroded. Pedal linkage binding.
PULLING OR GRABBING
Defective master cylinder. Defective caliper. Grease or fluid on linings. Defective brake lines. Metering valve malfunctioning. Power unit malfunctioning. Defective rotor. Loose or broken front end parts. Defective rear drum. Unmatched tires. Loose or broken rear springs.
PEDAL GOES SLOWLY TO FLOOR
Air in system. Hoses or lines soft (expand under pressure) or damaged. Master cylinder primary cup damaged, bore worn, or corroded. Improper fluid. Bleeder screw open.
NOISE, CHATTER, OR PULSATION
Defective rotor. Disc pad or rotor out of parallel. Anti-rattle spring missing or out of position. Excessive clearance between disc pad and caliper. Disc pad rubbing on caliper housing. Caliper binding on mounting bolts. Rear drums defective. Wheel bearings loose. Wheel nuts loose. Wear sensor contacting rotor
DRAGGING BRAKES
Defective brake line or hose. Defective master cylinder. Residual pressure valve installed in outlet to front brakes. Power unit push rod out of adjustment. Sticking pedal linkage. Metering valve defective or incorrectly installed. Defective power unit. Defective caliper.
REAR BRAKES SKIDDING (HARD PEDAL APPLICATION)
Defective proportioning valve.


Friday, March 29, 2013

BMW 320i 530i 630Csi 1977 Brake Repair Guide

DESCRIPTION
Brake system is hydraulically operated. System uses both a tandem master cylinder and power brake unit. 530i and 630CSi models have 4 piston ATE  front disc brakes and 2 piston ATE rear brakes. 320i models are equipped with 2 piston ATE front disc brakes and drum rear brakes. Parkng brake is lever actuated and cable operated. On 530i and 630CSi models, brake shoes work against a drum machined in rear disc brake rotor/hub. On 320i models, shoes lock against rear brake drum. All models are equipped with a brake pressure regulator to reduce line pressure to rear brakes.
ADJUSTMENT
Disc Pads
320i - Raise vehicle. Release parking brake. Using special tool 34 2 000 (or equivalent wrench), tighten brake shoes by turning left cam counterclockwise and right cam clockwise. Loosen cam 1/8 turn or until wheel is just free to turn.
PARKING BRAKE
530I & 630CSi - 1) Release parking brake lever, raise and support vehicle, and remove rear wheels. Insert a brake adjusting tool through .6" hole in rotor, turn adjuster until rotor can no longer be rotated, then back off adjuster 2 or 3 teeth.
2) Work inside drive compartment, tighten adjustment nuts on lever until parking brake holds vehicle securely before fifth ratchet stop is reached.
320i - 1) Raise and support rear of vehicle. Fully release parking brake. Tighten brake shoes until wheel is locked. Back off adjusters about 1/8 turn or until wheel can just barely turn.
2) Work in inside drivers compartment and tighten nuts on lever until parking brake holds vehicle securely before fifth ratchet stop is reached.
HYDRAULIC SYSTEM BLEEDING
NOTE - Manufacturer recommends replacing brake fluid in 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 to escape, then close bleeder screw. Continue operation until all air has been expelled from system. NOTE - On front wheel four piston calipers, bleed lower inboard screw before bleeding lower outboard screw.
REMOVAL & INSTALLATION
DISC PADS
Removal - Raise and support vehicle and remove wheels. Drive out retaining pins toward inside of vehicle
Fig. 1 Piston Alignment for Dual Piston
Calipers
and remove cross spring. Using an extractor tool, remove disc pads from caliper assembly. If disc pad thickness (including backing) has been worn to .080" (.02 mm), replace pads. Only replace pads in sets.
Installation - 1) Using a cylinder brush, clean guide surface and support surface in caliper. Siphon sufficient fluid from master cylinder reservoir to prevent overflowing then press pistons to bottom of bores.
2) On rear two piston calipers, ensure machined position of piston face makes a 20 degree 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 - Drain brake fluid from master cylinder reservoir. Remove caliper mounting bolts. Disconnect disc pad wear indicator electrical lead. Disconnect brake fluid inlet lines. Lift caliper off rotor.
Installation - Reverse removal procedure and bleed hydraulic system.
ROTOR
Removal: 530i; 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.
NOTE - Both brake rotors must be replaced at the same time.
Installation - To install, reverse removal procedure. Tighten all bolts and fittings evenly. Bleed hydraulic system if necessary. Adjust front wheel bearings. See Wheel Bearing Adjustment in WHEEL ALIGNMENT Section.
Removal: 320i & 630CSi; Front - Raise and support front of vehicle. Separate bracket from strut. Remove caliper and tie out of way with brake line still connected. Remove mounting bolt from hub and take off rotor.
NOTE - Inboard vented brake discs are balanced, DO NOT move or replace balance clips.
Installation - To install, reverse removal procedure.
Removal 530i & 630CSi; Rear - Raise vehicle and support on safety stands. Remove tire and wheel. Remove caliper and support out of way leaving brake line connected. Slip brake line out of clamp. Take out mounting bolt and remove brake rotor.
NOTE - Both rotors must be replaced at same time. Also, inboard vented brake disc are balanced, DO NOT move or replace balance clips.
Installation - To install, reverse removal procedure.
PARKING BRAKE SHOES
Removal - With rear caliper and rotor removed, disconnect lower return spring using brake spring pliers. Turn retaining spring 90 degrees using removal tool, then set spring aside. Pull brake shoes apart at bottom and lift upward
Installation - Reverse removal procedure and adjust parking brake shoes and cables.
BRAKE DRUM
Removal & Installation: 320i; Rear - Loosen brake adjuster cams. Remove countersunk Allen bolt and slide off brake drum. To install, reverse removal procedure and note: If one brake drum is reground, drum on other side must also be machined.
BRAKE SHOES
Removal: 320i; Rear - Remove brake drum. Disengage mounting spring, retainer, and pin from each shoe. disconnect bottom return spring. Pull shoes apart and out of wheel cylinder . Disconnect parking brake cable and remove brake shoes. If brake shoe lining was worn to .118" (3.0 mm) or less, replace brake shoes.
Installation - Reverse removal procedure and note: Connect long end of spring between parking brake lever and brake shoe.
WHEEL CYLINDER
Removal: 320i; Rear - Remove brake drum. Disconnect brake fluid inlet line. Remove wheel cylinder
Fig. 2 Exploded View of 320i Rear Wheel Cylinder
bleeder valve. Remove cylinder, mounting bolts and take off cylinder being careful not to drop brake fluid on brake shoes.
Installation - To install, reverse removal procedure and make sure to bleed brake system.
MASTER CYLINDER
Removal - Siphon off brake fluid from reservoir. On 320i models, disconnect clutch hose connection. On 630CSi models, remove air cleaner. Disconnect all hydraulic lines from master cylinder. Remove nuts mounting master cylinder. Remove nuts mounting master cylinder to power booster. On 320i models, remove nuts mounting master cylinder support to inner fender panel. Remove support and master cylinder.
Installation - To install, reverse removal procedure and note: Make sure "O" ring on master cylinder is not damaged. An imperfect fit will not allow correct vacuum build-up.
POWER BRAKE UNIT
NOTE - Mixture control unit must be removed to take off power brake unit (with master cylinder).
Fig. 3 Disassembled View of Dual Piston Rear Disc
Brake for 530i & 630CSi. Front Caliper for
320i is Similar
Removal: 320i - 1) Remove air intake ducting. Remove 3 screws located in top of control unit. Spread open cable clips. Remove wire holder. Lift up mixture control unit and retain piston with fingers until it can be tapped into place. Disconnect remaining vacuum lines. Remove unit mounting nuts and lift off unit.
2) Siphon out brake fluid from reservoir. Disconnect push rod from brake pedal. Separate hydraulic lines from master cylinder. Also disconnect clutch hose.
3) Disconnect vacuum hose from brake unit. Remove brake unit mounting nuts and bolts. Separate master cylinder support from inner  fender panel. Slide master cylinder and power brake assembly from vehicle.
Installation - To install master cylinder and power brake assembly as a unit, reverse removal procedure.
Removal: 530i & 630CSi - Disconnect power brake push rod from brake pedal at clevis pin. Disconnect
vacuum hose at power brake unit. Disconnect and plug brake lines at master cylinder. remove brake unit at mounting bracket and slide entire unit out of vehicle
Fig. 4 Exploded View of 320 Rear Drum Brake Assembly
Installation - To install brake unit with master cylinder connected, reverse removal procedure. Bleed brake system after assembly is installed.
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 black 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.
OVERHAUL
Fig. 5  Four Piston Disc Brake Caliper Assembly  for 530i & 630CSi

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 assemble, 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 epxansion 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 piston 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
Fig. 6 Master Cylinder Primary Piston Assembly
Disassembly - Push i non 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 and position 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 thin coating of ATE brake paste. Install piston assemblies
Fig. 7 Master Cylinder Secondary (Front) Piston Assembly
into cylinder bore using a suitable guide sleeve (BMW 34 3 000) 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 1976 Models 6 Cylinder Brake Repair Guide

For:
3.0
530i

DESCRIPTION
Brake system is hydraulically actuated, using a tandem master cylinder and a power brake unit. All models use four wheel ATE disc brakes. Front brakes are four piston caliper type and the rear use two piston fixed caliper type and the rear use two piston fixed caliper type. Parking brake is cable actuated, operating conventional type brake shoes against a drum machined in rear disc brake rotor casting.
ADJUSTMENT
Disc Pads
Front and rear disc brake assemblies are self-adjusting, therefore, no adjustment in service is required.
Parking Brake
Release parking brake lever, raise and support vehicle, and remove rear wheels. Insert a brake adjusting tool through .6" hole in rotor, turn adjuster until rotor can no longer be turned, then back off adjuster two or three teeth. Working inside driver compartment, tighten adjustment nuts on lever until parking brake holds vehicle securely before fifth ratchet stop is reached.
HYDRAULIC SYSTEM BLEEDING
NOTE-Manufacture recommends replacing brake fluid in 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 to escape, then close bleeder screw. Continue operation until all air has been expelled from system. NOTE - On front wheel four piston calipers, bleed lower inboard screw before bleeding lower outboard screw.
REMOVAL & INSTALLATION
DISC PADS
Fig. 1 Piston Alignment - Calipers with Dual Piston
Removal - Raise and support vehicle and remove wheels. Drive out retaining pins toward inside of vehicle and remove cross spring. Using an extractor tool, 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 master cylinder reservoir to prevent overflowing, then press pistons to bottom of bores.
2) On rear two piston calipers, ensure machined position of piston face makes a 20 degree 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 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 motor 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 and note the following: Properly align holes in rotor with axle shaft flange. 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 spring 90 degrees using removal tool, then set spring aside. Pull brake shoes apart at bottom and lift upward.
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.
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, 3.0 - 1) Remove air cleaner and battery, disconnect oil reservoir from power steering (if equipped) and move to one side. Black brake fluid reservoir outlets and remove lines from master cylinder.
Fig. 2  Disassembled View of  Dual
Piston Rear Disc Brake
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 hydrauli lines from master cylinder marking positions for reassembly reference. Remove nuts retaining power unit to support and remove power unit.
Installation - To install, reverse removal procedure, bleed hydraulic system and check following adjustments: Adjust push rod (A) length to 14.49-14.53" (368-369 mm). Adjust pedal height (B) to 9.65" (245 mm). Adjust exposed depth of brake light switch plunger (C) to .240-.280" (6-7 mm). See Fig. 3.
Removal, 530i - Siphon some brake fluid from master cylinder. Unbolt coolant reservoir and position out of way. Disconnect brake pedal push rod shaft. disconnect vacuum hose at power brake unit (servo). Separate each brake line from master cylinder and mark each for reinstallation reference. Unbolt power brake unit holder and remove.
Installation - To install, reverse removal procedure, bleed hydraulic system, and check following adjustments: Adjust pedal height (B) 9.05" (230 mm) for manual transmission models and 8.66" (220 mm) for automatic transmission models. Adjust exposed depth of brake light switch plunger (C) to .200" (5 mm). See Fig. 3.
Fig. 3 Power Brake Unit Push Rod Measurement Locations

Check Valve Replacement - Check valve is located in power unit vacuum hoses, and remove valve. To install, reverse removal procedure, making sure arrow or black portion of valve face 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.
OVERHAUL
Brake Caliper
Fig. 4 Four Piston Front Brake
Caliper Assembly
Disassembly - With caliper removed from vehicle and disc pads removed from caliper, remove clampingDO NOT Separate caliper halves unless a leak is detected. To disassemble, remove expansion bolts, separate caliper halves, and remove sealing rings.
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 -
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 piston 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 an 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 and position of parts used.
Fig. 5 Master Cylinder Primary
Piston Assembly
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 thin coating of ATE brake paste. Install piston assemblies into cylinder bore using a suitable guide sleeve (BMW 34 3 000) 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 4 Cylinder Models 1976 Brake Repair Guide

DESCRIPTION
Brake system is hydraulically operated using a tandem master cylinder and a power brake unit. Front disc brakes consist of rotors attached to wheel hubs, and four piston fixed calipers attached to steering knuckles. Rear brakes are leading-trailing shoe/drum, type, using a dual piston wheel cylinder. Parking brake is cable operated, activating secondary shoes of rear brake assemblies.
ADJUSTMENT
FRONT DISC BRAKE PADS
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 an offset wrench (BMW 6038), tighten left eccentric nut counterclockwise and then right eccentric nut clockwise until wheel is locked. NOTE - Rotate tire while making sure adjustments. Loosen each adjuster until wheel is just free to rotate.
PARKING BRAKE
With rear brakes properly adjusted, pull back 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 are 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 air to escape, then close bleeder screw. Continue operation until 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
Fig. 1 Installed View of BMW 2002 Disc Brake and Caliper
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, 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
Fig. 2 Attaching Points of  Brake Caliper and
Hydraulic Lines
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 loose 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 brakes (if required).
REAR BRAKE SHOES
Removal - With brake drum removed, remove shoe spring at bottom of brake assembly and pull shoes out from wheel cylinder. Disconnect parking brake cable from lever, remove return spring and strut, and remove brake shoes.
Fig. 3 Exploded View of Rear Drum Brake Assembly

Installation - Reverse removal procedure and note the following: Make sure long end of upper return spring is installed between parking brake lever and brake shoe. Ensure brake shoe spring at bottom of assembly is installed behind support plate.
REAR BRAKE WHEEL CYLINDER
Removal - With brake drum removed, disconnect hydraulic line, and remove bleeder screw and wheel cylinder attaching bolts. Using an offset wrench (BMW 6038), turn brake shoe eccentric adjusting nuts until shoes are spread out from wheel cylinder as far as possible. Remove wheel cylinder maneuvering out of backing plate.
Installation - Reverse removal procedure, adjust brake shoes, and bleed hydraulic system.
MASTER CYLINDER
Removal - Siphon fluid as necessary from master cylinder reservoir. If necessary, remove air cleaner assembly. Disconnect hydraulic lines from cylinder, cap all openings, and mark lines for reassembly reference. Remove attaching bolts and separate master cylinder from power unit.
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 .002" (.051 mm), 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 portions 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 degrees in relation to one another.
OVERHAUL
FRONT DISC BRAKE CALIPER
Disassembly - 1) With caliper fitted to a vise, remove snap rings and pull out rubber protective caps. Take special care not to damage pistons.

Fig. 4 Disassembled View of BMW Disc Brake
2) Using suitable piston clamp (BMW 34 1 050), lock one piston into cylinder bore. Insert a small block of hard wood between other piston and flat surface of clamp. Apply light air pressure to inlet port and expel
Fig. 5 Forcing Piston From Position in Brake
Caliper
piston from cylinder bore.
3) Using sealing plate across bore of vacant cavity, force out second piston. Third and fourth pistons are removed in a like manner. Using a plastic instrument, dig seal from groove on cylinder bore.
NOTE - Manufacturer does not recommend separating caliper halve unless a leak is detected.
Cleaning & 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.
Reasembly - Reassemble caliper with new sealing rings and expansion bolts if halves were separated. Tighten caliper expansion bolts alternately and evenly from inside out. Coat pistons and sealing rings with ATE brake caliper 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 & 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. 
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
Fig. 6 Master Cylinder Primary (Rear) Piston Assembly
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.
Cleaning & 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 bore using a suitable guide.

Fig. 7 Master Cylinder Secondary (Front) Piston Assembly




Reassembly - To reassemble, reverse removal procedure and note the following: Coat all components with ATE brake paste. Ensure piston is fitted using sleeve tool (BMW 34 4 010). New piston seals are marked with paint rings; paint marks face away from each other. When installing stop screw, place pressure on piston. Always replace copper sealing ring under stop screw.