DESCRIPTION
Brake system is hydraulically operated, using a tandem master cylinder and a Master-Vac power brake unit. Front brakes are Girling-Sumitomo dual piston fixed caliper disc type, and rear brakes are leading-trailing shoe/drum type. Brake system is equipped with a proportioning valve to prevent premature locking of rear wheels. Parking brake is mechanically actuated, operating sliding wheel cylinders of rear brake assemblies.
ADJUSTMENT
BRAKE PEDAL
Loosen lock nut, turn push rod clevis, and adjust push rod length so that height of pedal, measured from pedal pad to floor is 8.11" (206 mm). NOTE - Make sure pedal stopper (stop light switch) does not contact pedal arm at this time. With push rod adjusted, adjust stop light switch until pedal height is reduced to 7.99" (203 mm).
FRONT DISC BRAKE PADS
Front disc brakes are self-adjusting, therefore, no adjustment in service is required.
REAR DRUM BRAKE SHOES
Rear drum brakes are self-adjusting (actuated by parking brake), therefore, no adjustment in service is required.
PARKING BRAKE
With parking brake lever fully released, make sure distance between wheel cylinder lever pin hole center and buffer plate on brake assembly backing plate is .453 - .492". Reduce play in linkage by turning adjusting nut on front parking brake operating rod.
REMOVAL & INSTALLATION
FRONT DISC BRAKE PADS
Removal - Remove tire and wheel. Remove clip, retaining pin, danger spring and remove pad with shim.
Installation - Depress piston into cylinder so new pad may be inserted. Install pad, shim, damper spring and retaining pin securing with clip. Depress pedal several times to position new pads.
FRONT DISC BRAKE CALIPER
Removal - With disc pads removed, disconnect hydraulic line from caliper and plug openings. Remove caliper mounting bolts and separate caliper from steering knuckle and rotor.
Installation - Reverse removal procedure, tighten caliper mounting bolts securely, and bleed hydraulic system
FRONT DISC BRAKE ROTOR
Removal - With caliper assembly removed, remove wheel hub dust cap, cotter pin, and adjusting nut. Remove wheel hub and rotor assembly, wheel bearing, and washer from spindle as an assembly. Remove bolts attaching rotor to wheel hub and detach rotor.
Installation - Reverse removal procedure and adjust front wheel bearings.
REAR BRAKE SHOES
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| Fig. 1 Rear Drum Brake Exploded View |
Removal - Remove tire, wheel and drum. NOTE - Should drum be difficult to remove. Remove clevis pin from wheel cylinder lever and disconnect handbrake cable. Remove backing plate rubber boot and loosen brake shoes, (adjust star downward). Some difficulty may be incurred due to adjuster lever. Remove return springs, mounting springs, clips and pins.
Installation - Reverse removal procedure and note the following: Apply brake grease (or equivalent) to wheel cylinder, backing plate, and adjusting plate sliding surfaces, also lubricate wheel cylinder lever fulcrum and ensure wheel cylinder assembly operates freely.
MASTER CYLINDER
Removal - Disconnect hydraulic lines from master cylinder, remove nuts attaching cylinder to power unit, and separate master cylinder from power brake unit.
Installation - Reverse removal procedure, adjust brake pedal height, and bleed hydraulic system.
POWER BRAKE UNIT
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| Fig. 2 Master Cylinder Reservoir, Body and Piston Assemblies |
Removal - Disconnect power unit push rod from brake pedal by removing clevis pin. Disconnect hydraulic lines from master cylinder, vacuum line from power unit, remove master cylinder mounting nuts, and remove master cylinder. Remove nuts attaching power unit to firewall, and remove power unit from engine compartment.
Installation - Reverse removal procedure, adjust brake pedal height, and bleed hydraulic system.
Check Valve Replacement - Check valve is located in vacuum line between intake manifold and power unit on firewall. To remove, disconnect retaining clip from firewall, remove hose clamps, separate hoses from valve, and remove check valve. To install, reverse removal procedure.
OVERHAUL
FRONT DISC BRAKE CALIPER
Disassembly - Clean exterior of brake caliper. Remove retaining ring and dust seal. Using a small block
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| Fig. 3 Exploded View of Front Disc Brake Caliper |
Cleaning & Inspection - Clean all parts in alcohol or brake fluid. CAUTION - DO NOT use mineral based solvents. Inspect caliper bores for wear, rust, corrosion or other damage; minor deposits or scratches may be removed with fine emery cloth. Check piston for wear or damage. NOTE - DO NOT use abrasives on piston plated surfaces.
Reassembly - NOTE - Manufacturer recommends replacing rubber parts whenever caliper is being overhauled. Coat piston seal with rubber grease and install into caliper bore. Install dust seal on piston, insert piston into caliper, and install remaining ring. Install opposite piston assembly in same manner.
REAR WHEEL CYLINDER
Disassembly - Remove snap ring and dust cover. Withdraw piston and seal assembly, adjuster wheel,
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| Fig. 4 Disassembled View of Wheel Cylinder |
Cleaning & Inspection - Clean all parts in alcohol or brake fluid. CAUTION - DO NOT use mineral based solvents. Check all parts for wear or damage; replace parts as necessary. Check clearance between cylinder bore and piston, if clearance exceeds .006", replace cylinder or piston as necessary. Check spring for damage or distortion. NOTE - Manufacturer recommends replacing seal whenever wheel cylinder has been disassembled.
Reassembly - Reverse disassembly procedure and note the following. Apply rubber grease to all parts when reassembling to prevent damage.
MASTER CYLINDER
Disassembly - Remove reservoir filler caps, drain brake fluid, and remove secondary piston stop bolt. Remove snap ring and withdraw primary piston, secondary piston and return springs. Remove valve caps and withdraw check valve assemblies. NOTE - Do not remove reservoirs unless necessary
Cleaning & Inspection - Clean all parts in alcohol or brake fluid and inspect for wear or damage. Check clearance between cylinder bore and pistons, if clearance exceeds .006", replace cylinder bore and piston as necessary NOTE - Manufacturer recommends replacing piston cups, gaskets, and valves whenever master cylinder has been disassembled.
Reassembly - Reverse disassembly procedure and note the following: Apply rubber grease to all rubber parts and brake fluid to remaining parts when assembling to prevent damage.
POWER BRAKE UNIT
Disassembly - 1) Place power unit in a soft jawed vise with operating rod pointing up. Scribe alignment marks on front and rear shells to assure reassembly in original position. Remove operating rod lock nut and clevis, then remove dust boot from rear shell.
2) Place a suitable wrench (ST08080000) over rear shell mounting studs. Press down on wrench while rotating diaphragm plate assembly, diaphragm spring and push rod assembly. Pry off retainer and remove bearing and valve body seat from rear shell.
3) Remove diaphragm from diaphragm plate assembly, then pry off air silencer retainer and remove silencer and filter. Rotate diaphragm plate assembly until valve plunger key slot is down, the npress in on plunger and shake out stop key. Remove reaction disc from plate assembly. Detach flange from front shell and remove plate and seal assembly
Cleaning & Inspection - Clean all parts in denatured alcohol and blow dry with compressed air.
Reassembly - Reverse disasembly procedure and note the following: Apply a thin coat of silicone grease to parts before installation. When assembling front shell to rear shell ensure marks made at disassembly are aligned. After reassembly, measure distance from master cylinder mounting surface to end of power unit push rod; distance should be .38-.39" (9.8 - 10.0 mm), if distance is not to specifications, correct by adjusting end of push rod
