DESCRIPTION
Brake system is hydraulically operated, using a tandem master cylinder and a Master-Vac power brake unit. Front brakes are Akebono-Lockheed SC disc type, and rear brakes are leading-trailing shoe/drum type. A proportioning valve is used in brake system to prevent premature locking of rear brakes. Parking brake is cable and lever actuated, operating sliding wheel cylinders of rear brake assemblies
ADJUSTMENT
BRAKE PEDAL HEIGHT & FREE PLAY
Adjust brake light switch bolt until end face is flush with front face of bracket, then tighten lock nut. Adjust pedal stopper until pedal height, measured from pedal pad to floor, is 7.284" (185 mm). Adjust master cylinder push rod length until free play, measured at pedal, is .039 - .197" (1-5 mm).
FRONT DISC BRAKE PADS
Front disc brakes are self-adjusting, therefore, no adjustment in service is required.
REAR BRAKE SHOES
With parking brake fully released, depress brake pedal several times so that shoes are settled to normal positions. Turn adjusting cap on backing plate until shoes lock against drum. Loosen adjusting cam until drum is just free to rotate.
PARKING BRAKE
With rear brake shoes adjusted, adjust all slack from rear parking brake cable adjuster.NOTE - Make sure cables do not pull on wheel cylinders. Adjust front parking brake cables so that reaer wheels are locked when lever is pulled to the sixth or seventh ratchet stop. With cables adjusted, release parking brake and ensure rear wheels rotate freely.HYDRAULIC SYSTEM BLEEDING
Attach a bleed tube to bleeder screw and immerse opposite end of tube in a container partially filled with brake fluid. Open bleeder screw 3/4 turn, depress pedal, close bleeder screw, and allow pedal to return slowly. Continue operation until air bubbles are no longer seen in discharged fluid. Repeat procedure on remaining brake lines until all air is bled from system. Bleeding sequence is: Master cylinder first, rear brakes second, and front brakes last.
REMOVAL & INSTALLATION
FRONT DISC BRAKE PADS
Removal - Remove tire and wheel. Remove damper clip from caliper plate. Withdraw outer pad. Force plate inward and extract inner pad.
Installation - Wipe piston surface and caliper cavity clean. Push piston into caliper bore and install new pads. NOTE - Pads must be replaced in sets of four. Insert damper clip. Install tire and wheel.
FRONT DISC BRAKE CALIPER
Removal - Raise and support vehicle and remove tire and wheel assembly. Disconnect hydraulic line from caliper and plug openings. Remove bolts securing caliper to steering knuckle and remove caliper.
Installation - Reverse removal procedure, tighten mounting bolts securely, and bleed hydraulic system.
FRONT DISC BRAKE ROTOR
Removal - With caliper assembly removed, remove hub dust cap, adjusting cap, adjustment nut and washer. Slide hub and rotor assembly from spindle taking care not to lose outer wheel bearing. Remove bolts attaching rotor to hub, then separate.
Installation - Reverse removal procedure, tighten rotor attaching bolts securely, and adjust wheel bearings.
REAR BRAKE SHOES
Removal - Raise and support vehicle, remove tire and wheel assembly, and remove brake drum. Disconnect anti-rattle springs (if equipped) and shoe return springs, then remove brake shoes from backing plate. If necessary, remove bolts securing adjuster to backing plate and remove adjuster assembly.
Installation - Reverse removal procedure and note the following: Apply grease to sliding areas of backing plate and adjuster, taking care not to contaminate linings. When installed, adjust brake shoes, parking brake, and bleed hydraulic system.
REAR BRAKE WHEEL CYLINDER
Installation - Reverse removal procedure and note the following: After wheel cylinder is installed, measure wheel cylinder sliding resistance using a pull gauge; resistance should be 4.4-15.4 lbs. (2.0 - 7.0 kg.). Install brake shoe assemblies and bleed hydraulic system.
MASTER CYLINDER
Removal - Disconnect and plug front and rear hydraulic lines from master cylinder and drain brake fluid from cylinder. Remove master cylinder attaching nuts and lift off master cylinder.
Installation - Reverse removal procedure and bleed hydraulic system.
POWER BRAKE UNIT
Removal - With master cylinder removed, disconnect vacuum line from power unit. From inside vehicle, disconnect pedal return spring, push rod from brake pedal, and power unit mounting nuts. Remove power unit from engine compartment.
Installation - Reverse removal procedure, adjust pedal height and free play, and bleed hydraulic system.
Check Valve Replacement - Check valve is located near identification plate on firewall. To remove, disconnect clip, remove hose clamps, separate hoses from valve, and remove valve. To install, reverse removal procedure.
OVERHAUL
FRONT DISC BRAKE CALIPER
Disassembly - Remove anti-rattle clip from caliper plate and remove disc pads, Remove tension springs and remove cylinder from caliper plate. Remove piston from cylinder by applying air or hydraulic pressure to fluid inlet hole. Remove wiper seal and retainer.
Cleaning & Inspection - Clean all parts in alcohol or brake fluid and inspect for wear or damage. Light deposits may be removed from cylinder bore using fine emery paper. CAUTION - DO NOT polish piston plated surfaces with emery paper; replace piston if severely rusted or corroded.
Reassembly - NOTE - Manufacturer recommends replacing rubber seals whenever caliper has been disassembled. Lubricate all parts with rubber grease. Install seal into groove in cylinder. Install wiper seal and retainer. Insert piston into cylinder until face of piston head is almost flush with retainer. Install cylinder to caliper plate and secure with torsion springs. Install disc pads and anti-rattle spring.
REAR WHEEL CYLINDER
Disassembly - Remove snap ring and dust boot, then withdraw piston and seal assembly from cylinder bore. Remove seal from piston.
Cleaning & Inspection - Clean and dry all parts and inspect for wear or damage. Measure clearance between piston and cylinder bore; if clearance exceeds .006" (.15 mm), replace piston or cylinder as required.
Reassembly - Reverse disassembly procedure and note the following: Apply a thin coat of rubber grease to all parts when assembling wheel cylinder
MASTER CYLINDER
Disassembly - Remove reservoir cap and drain fluid. Remove dust cover, retaining ring and piston stop screw. Remove washer, primary piston assembly, secondary piston assembly and return spring. Remove valve plugs and remove check valves. NOTE - Do not remove master cylinder reservoir tanks; if removed new tanks must be reinstalled.
Cleaning & Inspection - Clean all parts in alcohol or brake fluid, and inspect for wear or damage; replace parts as required. Check clearance between cylinder bore and piston; if greater than .006" (.15 mm) replace cylinder or piston as required. NOTE - Manufacturer recommends replacing cylinder cups and valves whenever master cylinder has been disassembled.
Reassembly - Coat all parts with clean brake fluid and reverse disassembly procedure.
POWER BRAKE UNIT
Disassembly - 1) Place power unit in a soft jaw vise with operating rod pointing up. Scribe alignment marks on front and rear shells to assure reassembly in original position. Remove operating rod clevis, lock nut and dust boot.
2) Place Master-Vac wrench (ST08080000) over rear shell mounting stud. Press down on wrench while rotating counterclockwise and separate rear shell from front shell, then remove diaphragm plate assembly, diaphragm spring and push rod assembly. Pry off retainer and remove bearing and valve seal from rear shell.
3) Remove rubber diaphragm from diaphragm plate assembly, then pry off air silencer retainer and remove silencer and filter. Rotate plate assembly until valve plunger key slot is down, then press 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. Inspect front and rear shells for wear or damage. If slight rust is found on inside surface shell,, polish clean with fine emery cloth. Inspect all parts for cracks, nicks, distortion or other damage and replace as necessary.
Reassembly - Reverse disassembly procedure and note the following: Apply a thin coat of silicone grease to parts before reassembly. When assembling front shell to rear shell, ensure marks made during disassembly are aligned. After reassembly, measure distance from master cylinder mounting surface of power unit 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 tip of push rod.
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