Disc Brake System Chevrolet Corvette C4

ANTI-LOCK BRAKE SYSTEM SAFETY PRECAUTIONS

1. NEVER open a bleeder valve or loosen a hydraulic line while ABS is pressurized.
2. NEVER disconnect or reconnect any electrical connectors while ignition is on. Damage to ABS control unit may result.
3. ONLY use specially designed brake hoses/lines on ABS equipped vehicles.
4. DO NOT tap on speed sensor components (sensor, sensor rings). Speed rings must be pressed into hubs, NOT hammered into hubs. Striking these components can cause demagnetization or polarization, affecting the accuracy of the speed signal returning to the ABS control unit.
5. DO NOT mix tire sizes. Increasing the width, as long as tires remain close to the original diameter, is acceptable. Rolling diameter must be identical for all 4 tires. Some manufacturers recommend tires of the same brand, style and type. Failure to follow this precaution may cause inaccurate wheel speed readings.
6. DO NOT contaminate speed sensor components with grease. Only use recommended coating, when system calls for an anti- corrosion coating.
7. When speed sensor components have been removed, ALWAYS check sensor-to-ring air gaps when applicable. These specifications can be found in each appropriate article.
8. ONLY use recommended brake fluids. DO NOT use silicone brake fluids in an ABS equipped vehicle.
9. When installing transmitting devices (CB's, telephones, etc.) on ABS equipped vehicles, DO NOT locate the antenna near the ABS control unit (or any control unit).
10. Disconnect all on-board computers, when using electric welding equipment.
11. DO NOT expose the ABS control unit to prolonged periods of high heat (185°F/85°C for 2 hours is generally considered a maximum limit).

ANTI-LOCK BRAKE SYSTEM

The Bosch Anti-Lock Brake System (ABS) increases vehicle steerability, directional stability and optimum deceleration in severe braking conditions on most road surfaces. The ABS monitors wheel speed and controls brake line pressure to eliminate uncontrolled skidding. This performance supplies the vehicle with maximum controllability.

The ABS consists of an Electronic Brake Control Unit (EBCU), modulator valve, lateral acceleration switch and wheel speed sensors. ABS system utilizes a 3-way hydraulic circuit; one circuit for each front wheel and a common circuit for rear axle.

Components unique to the anti-lock brake system are covered in a separate article. See appropriate ANTI-LOCK BRAKE SYSTEM article as listed below.

1. «ANTI-LOCK BRAKE SYSTEM»(/chevrolet/corvette/c4-1984-1998/remont/anti-locktraction-control/#anti-lock-brake-system) - 1991
2. «ANTI-LOCK BRAKE SYSTEM»(ref-45074) - 1990

BRAKE BOOSTER

This booster is a single diaphragm vacuum suspended unit. In a normal operating mode, with the service brakes in the released position, the booster has vacuum on both sides of its diaphragm.

When the brakes are applied, air at atmospheric pressure, is admitted to the back side of the diaphragm to provide power assist. Tie rods extend through the booster and are attached to the cowl on one end and the master cylinder on the other.

DISC BRAKES

The Corvette features a 4 wheel disc brake system. The system incorporates finned aluminum calipers mounted to nodular iron reaction brackets. The front calipers are two piston type and the rear calipers are single piston type.

Hydraulic pressure is converted into friction through a clamping action on the rotor by the caliper and friction pads. The inboard pads utilize a wear sensor. The sensor emits a high pitched squeal when linings need replacement. The rotors are finned, Gray cast iron.

PARKING BRAKE

The parking brake assembly is an integral part of the rear calipers. When the parking brake is applied, the lever on the caliper causes the pushrod, actuating collar and clamp rod assembly to be moved outward and the caliper to slide inward. This action forces the linings against the brake rotor. The parking brake system is independent of the hydraulic braking system.

MASTER CYLINDER

The master cylinder is an aluminum plastic composite with an integral proportioning valve and warning switch. The master cylinder has separate front and rear plastic reservoirs.

When the brake pedal is applied, force is transferred through the push rod to the master cylinder primary piston, which moves forward. Under normal conditions, the combination of hydraulic pressure and the force of the primary piston spring move the secondary piston forward at the same time.

When the pistons have moved forward so that their primary cups cover the by-pass holes, hydraulic pressure is built up and transmitted to the front and rear calipers.

HYDRAULIC BRAKE BLEEDING

SERVICING METERING VALVE

The combination proportioning valve/warning switch is integral with the master cylinder and requires no service for brake bleeding.

BENCH BLEEDING MASTER CYLINDER

Note. Bleed tubes must have a residual pressure check valve installed to keep tubes from siphoning brake fluid.

1. Clamp master cylinder in vise by mounting flange. Install and tighten threaded end of bleed tubes in outlet ports of master cylinder with opposite end of bleeder tube in reservoir. Fill reservoir with clean brake fluid so that bleed tube ends are submerged in brake fluid.
2. Slowly compress and release piston assemblies until bubbles cease to appear in brake fluid. Remove tubes and plug master cylinder outlets to keep fluid from draining.

BLEEDING MASTER CYLINDER ON VEHICLE

1. Depressurize ABS system. Remove power brake reserve by applying brakes several times with the ignition off until all reserve is depleted. Ensure fluid level in master cylinder reservoir is adequate.
2. Loosen front hydraulic line on master cylinder and allow fluid to fill the master cylinder until it begins to flow from the front line connector port.
3. Tighten front brake line. Depress and hold the brake pedal slowly one time and hold. Loosen the front brake line connection at the master cylinder to purge air from the cylinder. Tighten the brake line and then slowly release the brake pedal.
4. After waiting fifteen seconds, repeat the process, including the fifteen second wait, until all air is purged from the forward end of master cylinder. Repeat process for rear brake line connection.

MANUAL BLEEDING

Note. When bleeding the rear brakes, the front of the vehicle may have to be raised to position the bleeder valves of the rear calipers at the top of the caliper to prevent air from being trapped in the caliper.

Note. Ensure that fluid level in master cylinder is adequate at all times during bleeding procedure.

1. Depressurize ABS system. Depress brake pedal several times to deplete vacuum reserve in brake booster. Fill master cylinder with clean brake fluid.
2. Install bleeder hose to right front caliper bleed screw. Submerge other end of hose in clean glass jar partially filled with clean brake fluid.
3. Depress brake pedal slowly through its full travel and hold. Open bleed screw 3/4-1 turn. Close bleed screw. Release brake pedal. Repeat procedure until brake fluid shows no signs of air bubbles.
4. Repeat procedure for other calipers after right front in the following sequence: right rear, left rear, left front.

PRESSURE BLEEDING

Note. When bleeding the rear brakes, the front of the vehicle may have to be raised to position the bleeder valves of the rear calipers at the top of the caliper to prevent air from being trapped in the caliper.

1. Depressurize ABS system. Wipe master cylinder and reservoir with clean dry shop towels to prevent dirt from falling into reservoir.
2. Using appropriate adapter, install pressure bleeding equipment to master cylinder. Ensure pressure tank is at least 1/3 full. Install bleeder hose to right front bleed screw. Submerge other end of hose in clean glass jar partially filled with clean brake fluid.
3. Charge pressure bleeder to 20-25 psi. (1.41-1.75 kg/cm 2 ). Open release valve on pressure bleeder. Open bleed screw 3/4-1 turn. Close bleed screw when brake fluid is clear and free of bubbles. Bleed remaining calipers in the following sequence: right rear, left rear, left front.
4. Remove pressure bleeding tool. Ensure fluid level in reservoir is adequate.

BLEEDING PRESSURES

BLEEDING PRESSURE

BLEEDING SEQUENCE

BLEEDING SEQUENCE

Disc brakes are self-adjusting. Caliper piston seals are designed to retract pistons just enough to allow brake lining to lightly brush rotor without any drag. Sliding caliper design compensates for any lining wear.

FRONT WHEEL BEARING

A single unit hub and bearing assembly is bolted to the front knuckle. The hub and bearing assembly is a sealed unit and no adjustment is required.

MASTER CYLINDER PUSH ROD

The master cylinder push rod is adjusted at factory and requires no adjustment.

Adjusting Parking Brake

The parking brake system is self adjusting and requires no periodic adjustments. If caliper or parking brake cables have been removed or disconnected, pull up on parking brake lever 3 times with a force of 50 lbs. (220 N.m). Parking brake is properly adjusted when lever pulls up 7-9 ratchet clicks. Ensure that caliper levers are on their stops when park brake is released.

Scheme 1

1. Remove driver's seat cushion, parking brake lever cover and screws. Fabricate a hook on end of a solid wire.
2. Using wire hook, hold drive pawl so it is disengaged from drive sector. Insert a nail through hole in anchor plate to retain drive pawl in disengaged position. (Scheme 1)
3. Move lever until it aligns with lock pawl. Depress button on lever and move lever to down position. Visually inspect to see that anchor plate is against stud. If anchor plate is not against stud, repeat procedure as needed.

Note. Brake pads must be new or within .006" (0.15 mm) thickness of each other. Parking brake adjustment will not be accurate with heavily tapered pads. Parking brake free play should only be made if caliper has been disassembled. Free play adjustment will not correct a condition such as levers not returning to their stops.

Cable Free Play

1. With parking brake automatic adjuster disabled, have an assistant apply a light brake pedal pressure (enough to stop rotor from turning by hand). Apply pressure to caliper lever. (Scheme 2) Free play between caliper lever and housing must be.024-.027" (.61-.69 mm).
2. If free play is incorrect, remove adjustment screw and clean threads. Coat threads with adhesive. Screw in adjustment screw far enough to obtain proper free play between caliper lever and caliper housing. Have assistant release brake pedal, apply brake pedal firmly 3 times. Recheck free play and adjust if necessary.

Scheme 2

REAR WHEEL BEARING

A single unit hub and bearing assembly is bolted to the rear knuckle. The hub and bearing assembly is a sealed unit and no adjustment is required.

Lateral Runout

Install two wheel lug nuts to ensure proper disc alignment. Clamp a dial indicator to caliper so it contacts rotor at a point about 1/2" from outer edge. Turn rotor one full revolution. Check indicator reading. If reading exceeds .006 in. (.15 mm), refinish or replace rotor.

Parallelism

Check thickness of rotor at 4 or more points around edge of rotor. Make all measurements the same distance from edge. If thickness varies over .00005 in. (.013 mm), refinish or replace rotor.

CLEANING & INSPECTION

Note. When servicing brake parts, do not create dust by grinding or sanding brake linings or by using compressed air. Use water dampened shop towel to remove dirt and dust from brake parts during disassembly.

DISC PAD INSPECTION

Inspect brake pad linings every 6000 miles or whenever wheels are removed. Replace, in complete sets only, any linings that are worn to within 1/32 in. of the shoe.

REMOVAL & INSTALLATION

Removal

1. Disconnect negative battery cable. Remove ECM and ECM housing bracket bolt from under instrument panel. Disconnect cruise control cable from servo and bracket. Disconnect pressure sensor connector and vacuum hose.
2. Remove nuts attaching master cylinder to booster tie rods and remove master cylinder. Disconnect push rod (part of valve assembly) from brake pedal. Remove nuts from booster tie rods and remove booster, ECM brackets and seal as assembly.
3. Remove assembly from brake pedal bracket and brake pedal. Inspect seals and mounting-sealing surfaces for damage. Repair/replace as needed.

Installation

1. Attach seals to brackets. Install complete power booster and bracket assembly to brake pedal bracket and brake pedal.
2. Install booster tie rod nuts, and tighten to 15 ft. lbs. (21 N.m). To complete installation, reverse removal procedure. Tighten master cylinder nuts to 13 ft. lbs. (18 N.m). Tighten ECM housing bracket mounting bolt to 18 ft. lbs. (25 N.m).
3. Clear ALL ECM and CCM codes, unlock radio Delco-Loc II security function (if equipped) and check VATS (PASS-KEY) program for proper operation.

DISC BRAKE CALIPERS & PADS - FRONT

1. Depressurize ABS system. Remove 2/3 of brake fluid from reservoir. Lift and support vehicle. Mark relationship of wheel to axle. Remove wheel. Reinstall 2 lug nuts to hold rotor in position.
2. Remove circlip from retainer pin and remove pin. Pivot caliper away from rotor and remove. If caliper is to be overhauled, remove inlet fitting and plug to prevent contamination. If caliper is not to be removed, place caliper on upper control arm to protect hose from damage.
3. Remove outboard shoe from caliper. Place large adjustable pliers or C-clamp over inboard pad and caliper housing to bottom pistons in bores. Clean all residue from mounting bracket and caliper shoe contact surfaces.

1. Install outboard shoe in caliper, ensure that shoe is flush with caliper housing. Install inboard shoe with wear sensor in caliper, ensure that shoe is fully seated into pistons.
2. Install caliper in mounting bracket over rotor and pivot into place. Install retainer pin into caliper mounting bracket by pushing down on caliper to compress bias springs. NOTE: There are two sets of retainer pins included in repair kit. One set is for standard calipers and the other is for heavy duty calipers. Ensure that the correct pins are installed. The circlip grooves are in different places on pin.
3. Install circlip on retainer pin. Install inlet fitting (if removed) with new gaskets and torque to 30 ft. lbs. (40 N.m). Bleed brake system if inlet hose was removed.

DISC BRAKE CALIPERS & PADS - REAR

1. Depressurize ABS system. Remove 2/3 of brake fluid from reservoir. Lift and support vehicle. Mark relationship of wheel to axle. Remove wheel. Reinstall 2 lug nuts to hold rotor in position.
2. Position "C" clamp over caliper and tighten clamp until piston bottoms in bore. (Scheme 3)
3. Remove and discard upper self-locking bolt. Rotate caliper on lower bolt and guide pin to expose pads. Remove pads. CAUTION: DO NOT attempt to remove caliper from vehicle without first disabling parking brake automatic adjuster. See «PARKING BRAKE»(/chevrolet/corvette/c4-1984-1998/remont/mechanical-hydraulic/#disc-brake-system) under ADJUSTMENTS.
4. To remove caliper, disable parking brake automatic adjuster. See «PARKING BRAKE»(/chevrolet/corvette/c4-1984-1998/remont/mechanical-hydraulic/#disc-brake-system) under ADJUSTMENTS. Remove caliper lever return spring. Disconnect parking brake cable from caliper lever and caliper bracket.
5. Remove and discard lower self-locking bolt. Disconnect inlet fitting and plug to prevent contamination. Clean mounting bracket and caliper housing outer legs of all residue. If guide pin dust boots are cracked or deteriorated, replace them with new ones.

Bottoming Piston In Bore. Scheme 3

Note. Caliper self-locking bolts must be replace with new bolts if loosened or removed from caliper mounting bracket.

1. Install outboard shoe in caliper mounting bracket. Install inboard shoe with wear sensor in the trailing position with forward wheel rotation.
2. Install new self-locking bolt in caliper and pivot caliper over shoe and pad assemblies. Spring on outboard shoe must not stick out through caliper opening. Adjust shoe position if necessary.
3. Install other new self-locking bolt in caliper and torque upper self-locking bolt to 26 ft. lbs. (35 N.m). Tighten lower self-locking bolt to 16 ft. lbs. (22 N.m). Bleed brake system if caliper or inlet fitting was removed.
4. Connect park brake cable to caliper bracket and lever. Install caliper lever return spring. If caliper was overhauled, parking brake free play must be adjusted. See «PARKING BRAKE»(/chevrolet/corvette/c4-1984-1998/remont/mechanical-hydraulic/#disc-brake-system) under ADJUSTMENTS. Enable parking brake automatic adjuster. See «PARKING BRAKE»(/chevrolet/corvette/c4-1984-1998/remont/mechanical-hydraulic/#disc-brake-system) under ADJUSTMENTS. Release parking brake.

DISC ROTOR

Note. Whenever caliper mounting bracket bolts are loosened or replaced, old bolts must be discarded and replaced with correct replacement bolts.

Remove and support caliper. On rear caliper, discard caliper self-locking bolts. Remove caliper mounting bracket bolts and discard. Remove rotor from hub.

1. To Install, clean off residual hardened bolt adhesive from mounting bracket threads, mounting bracket mating surface and knuckle mating surface. Install rotor on hub. NOTE: Heavy duty front rotors have directional cooling fins and are not interchangeable from left to right. Ensure that rotors are installed on correct side of vehicle.
2. Using new mounting bracket bolts, install mounting bracket to knuckle and torque bolts to specification. See «TORQUE SPECIFICATIONS»(/chevrolet/corvette/c4-1984-1998/remont/mechanical-hydraulic/#disc-brake-system__torque-specifications) table in this article. Recheck torque on both bolts after installation. Allow bracket bolt adhesive to cure two hours before driving vehicle.

Depressurize ABS system. Disconnect hydraulic brake lines and plug to keep out foreign matter. Remove nuts retaining master cylinder to brake booster. remove master cylinder.

Install master cylinder to brake booster studs. Torque attaching nuts to 15-25 ft. lbs. (20-34 N.m). Attach hydraulic lines and torque to 12-15 ft. lbs. (16-20 N.m). Bleed brake system. See HYDRAULIC BRAKE BLEEDING .

With master cylinder removed from vehicle, clamp master cylinder in vice by mounting flange. Grasp reservoir and pull off with rocking motion. Carefully pry grommet off master cylinder body using care not to damage boss or port on body.

Scheme 4

1. Lubricate new grommet inside and out with clean brake fluid. Lubricate inside neck on reservoir with clean brake fluid. By hand, press grommet into reservoir until grommet flange is flush against reservoir.
2. Install pilot (J-34121-1) in reservoir port on master cylinder body. Lubricate outside of pilot and body port with clean brake fluid. (Scheme 4) (Scheme 4): Installing Reservoir Using Pilot (J-24121-1) & Installer (J-24121-2)
3. Install reservoir and grommet assembly down over pilot. Position installer (J-34121-2), open end down, into reservoir, seated on boss around grommet. Using an arbor press, press reservoir and grommet assembly onto body until flange of grommet seats against body face.
4. Remove installer and pilot. Using installer, ensure that reservoir and grommet are firmly seated on cylinder body.

Disassembly

1. Remove vacuum check valve. Unscrew nuts approximately 1/2" back on tie rods, but do not remove. If shell halves stick together, pry them apart with a thin blade screwdriver using extreme care not to chip or otherwise damage either shell.
2. When bond between shells is broken, return spring will force front shell out against nuts. Then, holding shells together, completely remove nuts and coned springs. Remove front shell and return spring.
3. Remove grommet and front seal from front shell. Remove boot, tie rods and gasket from rear shell. Loosen bead of diaphragm from rear shell. Remove ends of tie rod boots from posts in rear shell and remove vacuum piston.
4. Remove diaphragm and tie rod boots from vacuum piston. Remove rear seal and washers on tie rod posts from rear shell. Remove output rod retainer and reaction disc.
5. Remove stop plate from vacuum piston by pressing on open end of stop plate and pulling on closed end. Remove valve assembly from vacuum piston.

Note. Use all components included in repair kits to service this booster. Lubricate parts, where indicated, with silicone grease. The torque values specified are for dry, unlubricated fasteners. If any hydraulic component is removed or brake line disconnected, bleed the brake system.

Reassembly

1. Lubricate outside diameter of new valve assembly and fit it into vacuum piston. Retain valve assembly by installing stop plate. Make sure stop plate is fully installed to locked position. Lubricate reaction disc and install in vacuum piston.
2. Fit new tie rod boots into holes in vacuum piston. Liberally coat insides of these boots with silicone grease. Lubricate outside diameter lip on diaphragm and fit diaphragm into vacuum piston.
3. Press new rear seal into rear shell and place washers on tie rod posts. Lubricate inside diameter of rear seal. Install vacuum piston assembly into rear shell. Push tie rod boots over rear shell posts and locate diaphragm bead around rear shell.
4. Install tie rods in rear shell. Position rear shell with parts assembled thus far in fixture (J-23456-51A). Install output rod and new retainer in vacuum piston. Lubricate output rod. CAUTION: DO NOT attempt to adjust domed screw on output rod. This has been correctly set at the factory and should not be disturbed.
5. Fit new front seal in front shell, metal face of seal facing out. Push seal into bottom. Locate return spring in mouth of vacuum piston. Install front shell on rear shell and other assembled parts using care not to unseat bleed of diaphragm NOTE: In the following step, use only original or genuine GM replacement nuts.
6. Press shells together by hand and install coned springs and nuts. Make sure coned springs are positioned correctly (Scheme 5) Uniformly tighten nuts until shells are.20" (5 mm) apart. Check that diaphragm is properly seated over rim of rear shell.
7. Tighten nuts to obtain correct dimension using gauge (J-35498). (Scheme 6) This dimension is measured across washer face on tie rod and nut, not across shell surfaces.
8. Lubricate grommet and vacuum check valve and install in front shell. Install gasket and boot onto rear shell. Be sure boot locates over flange on rear seal.

Proper Installation of Coned Spring In Power Brake Booster. Scheme 5

Assembling Shell Halves Of Power Brake Booster. Scheme 6

Exploded View of Single Diaphragm Power Brake Booster. Scheme 7

1. With caliper assembly removed from vehicle, pad interior of caliper with shop cloths. To remove pistons, direct compressed air into brake hose port. Always use eye protection during this step. WARNING: DO NOT attempt to catch or protect piston with fingers while applying compressed air. Injury may result. Always use eye protection when performing this step.
2. Inspect pistons for scoring, nicks, corrosion and worn or damaged chrome plating. Replace piston(s) if any of these defects are found. Remove piston boot from housing and discard.
3. Remove piston seals from groove in caliper bore with a piece of wood or plastic. DO NOT use a metal tool of any type, as damage to bore may result. Remove bleeder screw. Clean and inspect bleeder screw. Replace as necessary. Inspect guide pins. Clean or replace as necessary. Inspect caliper bores. If badly scored or corroded around seal area, replace with a new housing.

Scheme 8

1. Clean all parts not included in repair kit in denatured alcohol. Dry parts with non-lubricated dry compressed air. Check piston to bore fit by sliding piston into bore. Install cap and bleeder screw.
2. Lubricate new piston seal with clean brake fluid and install in caliper bore seal groove. Make sure seal is not twisted. Lubricate bore with clean brake fluid.
3. Insert pistons into caliper bore. By hand, push pistons to bottom of bore. Make sure boot is properly seated in groove around pistons and groove in caliper bores. Reinstall pads and caliper. Bleed brakes and road test vehicle.

1. Remove caliper assembly. Disconnect collar return springs from actuating collar. Remove actuating collar with assembled parts from caliper housing by pulling on both ends. (Scheme 9)
2. Remove clamp rod and compliance bushing from actuating collar. Remove boot retainers and push rod from actuating collar. Remove preload spring from retainer.
3. Pad interior of caliper with shop cloths. To remove piston, direct compressed air into brake hose port. Always use eye protection during this step. WARNING: DO NOT attempt to catch or protect piston with fingers while applying compressed air. Injury may result. Always use eye protection when performing this step.
4. Inspect piston for scoring, nicks, corrosion and worn or damaged chrome plating. Replace piston if any of these defects are found. Remove piston boot from housing by hand and discard.
5. Remove piston seal from groove in caliper bore. DO NOT use metal tool of any type, as damage to bore may result. Remove bleeder screw. Clean and inspect bleeder screw. Replace as necessary.
6. Inspect guide pins. Clean or replace as necessary. Inspect caliper bores. If badly scored or corroded around seal area, replace with a new housing.

Scheme 9

1. Clean all parts not included in repair kit in denatured alcohol. Dry parts with non-lubricated dry compressed air. Inspect all parts for damage and replace if necessary. Check piston to bore fit by sliding piston into bore. Install cap and bleeder screw.
2. Lubricate a new piston seal and caliper housing bore with clean brake fluid. Install in caliper bore seal groove. Make sure seal is not twisted. Insert pistons into caliper bore. Using hand pressure, push pistons to bottom of bore.
3. Install pushrod, new boots and new boot retainer to actuating collar. Lightly coat actuating collar with lubricant provided in repair kit. Clamp boot retainers firmly against actuating collar. Bend tabs on boot retainer to hold assembly together.
4. Install spring into boot retainer. Lightly coat clamp rod with lubricant in repair kit. Slide clamp rod through holes in boot and actuating collar. Ensure boot is against reaction plate on clamp rod. Lubricate new compliance bushing with provided lubricant and install to clamp rod.
5. Lubricate grooved bead of inner boot and boot groove in caliper housing with provided lubricant. Use remainder of lubricant to coat actuating collar, paying particular attention to center hole. Push clamp rod firmly to bottom of mating hole into piston.
6. Pull on actuating collar and seat inner boot into boot groove in caliper housing, ensure pushrod enters hole in caliper housing. Install new bleeder valve cap and bleeder valve in caliper housing. Tighten bleeder valve.
7. Install pivot pin and new nut to caliper housing. Tighten pivot pin nut. Lubricate caliper parking brake lever and pivot pin with provided grease. Install pivot pin seal. Install caliper parking brake lever and new sprag clip with teeth facing away from lever. Snap pivot pin seal over pivot pin.
8. Install 2 collar return springs to retainer (retainer must enter springs at end of second coil). Install adjustment screw into caliper housing until actuating collar is about parallel to piston bore face of caliper housing.
9. Lubricate 2 guide pins with grease provided in repair kit. Slide new boots on guide pins. Fill boots with provided grease. Assemble to mounting bracket. Make sure boots fit into grooves of guide pins and mounting bracket. Install caliper.

Note. It is not necessary to remove reservoirs to overhaul master cylinder. If reservoirs are damaged, remove and replace. See MASTER CYLINDER RESERVOIRS under REMOVAL & INSTALLATION.

1. Remove reservoir caps. Inspect caps for cracks or other damage and replace as necessary. Drain fluid from reservoir and pump cylinder to remove fluid.
2. Fully depress piston with wooden dowel and remove stop bolt. (Scheme 10) With cylinder depressed, remove piston retaining clip. NOTE: NEVER remove stop bolt unless pistons are fully bottomed in bore.
3. Remove primary piston. Gently tap open end of master cylinder on a piece of wood to dislodge the secondary piston.
4. Remove warning switch assembly being careful to retain the plastic body spring and probe as an assembly. Remove end plug and "O" ring. Gently tap the master cylinder body on a piece of wood to dislodge combination piston and spring.

Scheme 10

Note. If combination valve piston assembly is to be reused, DO NOT clean in any cleaning solution as the internal components are lubricated with special grease.

Inspection

1. Wash master cylinder body, bore, primary piston and secondary piston in denatured or isopropyl alcohol. Inspect piston assemblies and return springs.
2. Replace pistons if they are scored, galled, worn, cracked or broken. Replace springs if they are broken, bent, collapsed, distorted or fatigued.
3. Inspect cylinder bore for scoring, corrosion or wear. Cylinder bore is anodized. Wear on the anodized surface, as evidenced by lighter areas, is normal and not detrimental.

Note. DO NOT wash new combination valve in any cleaning solution as the internal components are pre-lubricated with special grease.

1. Coat bore of cylinder and piston assemblies with clean brake fluid. Install secondary and primary piston assemblies into cylinder. Press primary piston inward using wooden dowel and install piston retainer clip.
2. Depress piston inward until fully bottomed in cylinder bore and install stop bolt.
3. Install spring over capped end of combination valve. Lubricate the combination valve and bore with clean brake fluid. Install combination valve into bore and ensure valve is fully bottomed in cylinder. Install a new "O" ring lubricated with clean brake fluid over the threaded end of end plug.
4. Install end plug the end plug and torque to 15-22 ft. lbs. (20-30 N.m). Install warning switch. Install master cylinder reservoirs (if removed). See «MASTER CYLINDER RESERVOIRS»(/chevrolet/corvette/c4-1984-1998/remont/mechanical-hydraulic/#disc-brake-system) under REMOVAL & INSTALLATION. Bleed brake system.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

DISC BRAKE SPECIFICATIONS

DISC BRAKE ROTOR SPECIFICATIONS

See also:
• ANTI-LOCK BRAKE SYSTEM
• PARKING BRAKE
• TORQUE SPECIFICATIONS
• HYDRAULIC BRAKE BLEEDING