Disc & Drum Chevrolet Camaro II

AUTO ADJUSTER (DRUM BRAKE)

Automatic adjusters operate only when brakes are applied as car is moving in reverse. The link, which holds top of actuating lever stationary, forces lever to pivot on secondary shoe. This pivoting action forces pawl downward against tooth on adjuster screw.

If the lining-to-drum clearance is correct, the downward movement will stop before adjusting screw is turned. If clearance is too wide, secondary shoe will move outward. This allows pawl to move down enough to turn adjuster screw one notch. This brings lining-to-drum clearance back to correct specifications.

If adjuster screw is frozen or clearance is too great, an override device will prevent adjuster movement. This will prevent biding of automatic adjuster linkage.

Bendix Single Diaphragm

The Power Brake Booster is a self-contained, vacuum/hydraulic unit which uses engine manifold vacuum and atmospheric pressure to provide its power.

Vacuum power unit contains power piston assembly, which houses control valve, reaction mechanism, and return spring. Control valve consists of air valve, floating control valve assembly, and push rod. Reaction mechanism consists of reaction plate and levers. A vacuum check valve is mounted in front housing for connection to vacuum source.

Delco-Moraine Single Diaphragm

A combined vacuum-hydraulic unit which uses a combination of intake manifold vacuum and atmospheric pressure to provide power assist. Reserve vacuum supply and vacuum check valve allow several brake applications, with vacuum assist, after engine has stopped.

Unit is composed of 2 main sections, a vacuum power cylinder and a dual master cylinder. Vacuum power cylinder contains the power piston assembly, which houses the control valve, reaction mechanism, and power piston return spring.

Delco-Moraine Tandem Diaphragm

Unit is mounted on firewall and connected directly to brake pedal. A combination of vacuum and atmospheric pressure is used to provide power assist. Power cylinder houses power piston assembly, which contains primary and secondary diaphragms, pistons, floating control valve, reaction piston and disc.

Bendix Hydro-Boost II

Note. The Bendix Hydro-Boost II system is used on diesel engine equipped models.

The hydraulic brake booster consists of an open center spool valve and a hydraulic cylinder combined into a single housing. The power steering pump provides the hydraulic fluid pressure to operate both the power brake booster and power steering gear.

A dual master cylinder is bolted to the brake booster and is operated by a push rod projecting from booster cylinder bore. The brake booster also has a reserve accumulator system, which stores fluid under pressure to provide one power-assisted brake application when power steering pump fluid flow is interrupted.

DISC BRAKES - FRONT

Caliper is a single casting with 1 large piston inboard of disc rotor. It is mounted on the steering knuckle or a support bracket attached to front suspension. Brake rotors are cast iron with most models having ventilation fins separating the 2 braking surfaces. Some models use a groove machined in the braking surfaces to help control brake noise.

Disc brake pads are stamped steel with riveted linings. Most models use a wear sensor, a piece of spring steel riveted to the rear edge of inner brake shoe. The sensor produces a high pitched squeal when lining needs replacement.

DISC BRAKES - REAR

Note. Rear disc brakes are optional equipment on Chevrolet Camaro and Pontiac Firebird models.

Rear disc brakes are a single piston sliding caliper type. An integral parking brake is used, with an automatic adjusting provision. Brake rotors are made of cast iron, with 2 machined braking surfaces separated by cooling fins. On some cars, a groove is machined in center of the braking surface to aid in reducing braking noise.

DRUM BRAKES

Brakes are hydraulic single anchor and use Bendix type shoes. Anchor pins for brake shoes are fixed to backing plate and are non-adjustable. Automatic system is made up of a link, actuating lever, pawl and pawl spring. Pawl spring is mounted on secondary brake shoe. System uses an override pivot plate and spring to protect against binding linkage.

Note. Some models use an adjuster pawl with a separate blade to contact star wheel. This system does not use the override spring.

MASTER CYLINDER

All master cylinders are single cylinder with front and rear pistons. Master cylinders can have divided or common reservoirs that are integral with the piston cylinder.

Aluminum master cylinders have reservoirs that are removable from the piston cylinders. Front piston is operated by rear piston. In a divided reservoir, the larger reservoir feeds disc brakes.

A residual pressure valve is located in the master cylinder under outlet seat for drum brakes. This keeps small amount of pressure in drum brake circuit. Disc brake outlet does not have residual pressure valve and must not have any residual pressure or they will lock up.

On some master cylinders a stop screw is screwed in from outside of cylinder. This screw limits the return stroke of front piston.

Released Position (No Braking)

In this position, spool valve return spring holds spool valve open. In open position, spool valve provides unrestricted fluid flow between power steering pump and power steering gear. Fluid pressure is blocked from entering boost pressure chamber by lands on spool valve.

As fluid pressure increases with steering demand, it has no effect on boost pressure chamber. Boost pressure chamber is vented through spool valve, to pump return port, and back to power steering pump.

Braking Position

As brake pedal is depressed, it moves pedal rod and initiates movement of spool valve. This closes fluid return port to pump from boost chamber, and admits fluid into boost chamber from pressure port. Additional valve movement restricts flow between pump and steering gear, causing pump to increase fluid pressure to maintain flow rate to steering gear.

As fluid pressure increases in boost chamber, it forces piston forward actuating master cylinder piston, resulting in brake application. If fluid pressure is required for steering while braking, pump pressure will rise and spool valve will shift in an open direction allowing more fluid to flow to steering gear.

Reserve System

System consists of a charging valve, accumulator valve, and a compressed gas accumulator. System is open to pressure port of booster unit. Charging valve has an orifice and ball check. Fluid from pump passes through orifice in valve, and if pressure exceeds pressure in accumulator, it unseats ball check valve and enters accumulator. Ball check valve prevents reverse flow when accumulator pressure is greater than pump pressure.

Accumulator valve is a poppet type valve held closed by pressure stored in accumulator. An actuator on spool valve sleeve opens accumulator valve when a stop with no pump pressure is made that requires use of reserve pressure.

Fluid pressure can also enter accumulator from boost chamber through accumulator valve, when boost camber pressure exceeds accumulator pressure. A pressure relief valve vents accumulator to the pump return port when pressure in accumulator exceeds 1600 psi.

HYDRAULIC BRAKE BLEEDING

Hydraulic system bleeding is necessary any time air has been introduced into system. Bleed brakes at all 4 wheels if master cylinder lines have been disconnected or master cylinder has run dry.

Bleeding may be done either by using pressure bleeding equipment or by manually pumping brake pedal and using bleeder tubes.

SERVICING METERING VALVE

1. On disc brake equipped vehicles, the metering section of the combination valve must be deactivated before bleeding.
2. To hold the metering valve open to pressure bleed the front brakes, the valve stem must be pushed in or pulled out. Loosen front mounting bolt and install tool (J-23709) on the combination valve. (Scheme 3) Stem should be fully extended or depressed.

Deactivating Metering Valve for Bleeding (Typical). Scheme 3

BENCH BLEEDING MASTER CYLINDER

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

Scheme 4

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 reservoirs. Fill reservoirs with clean brake fluid so that bleed tube ends are submerged in brake fluid. (Scheme 4) (Scheme 4): Bleeding Master Cylinder With Bleeding Tubes Installed
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.

MANUAL BLEEDING

Note. Before bleeding system, exhaust all vacuum from power unit by depressing brake pedal several times. Bleed master cylinder if equipped with bleed screws, then bleed wheel cylinders or calipers in sequence.

1. Fill master cylinder. Install bleeder hose to first bleeder valve to be serviced. See «BLEEDING SEQUENCE»(/chevrolet/camaro/ii-1970-1987/remont/mechanical-hydraulic/#disc-drum) table. Place other end of hose in clean glass jar partially filled with clean brake fluid so end of hose is submerged in fluid.
2. Depress brake pedal slowly through its full travel. Open bleeder valve 3/4-1 turn. Close bleeder valve. Release pedal. Repeat procedure until flow of fluid shows no signs of air bubbles.

Note. Check fluid level in master cylinder frequently during bleeding to insure air does not enter system.

PRESSURE BLEEDING

Note. Before bleeding system, exhaust all vacuum from power unit by depressing brake pedal several times. Bleed master cylinder if equipped with bleed screws, then bleed wheel cylinders or calipers in sequence.

1. Clean master cylinder cap and surrounding area, then remove cap. With pressure tank at least 1/3 full, connect to master cylinder using adapters. (Scheme 5) Attach bleeder hose to first bleeder valve to be serviced. See «BLEEDING SEQUENCE»(/chevrolet/camaro/ii-1970-1987/remont/mechanical-hydraulic/#disc-drum) table. Place other end of hose in clean glass jar partially filled with clean brake fluid so end of hose is submerged in fluid.
2. Open release valve on pressure bleeder. Unscrew valve 3/4-1 turn noting fluid flow. When fluid flowing from cylinder to cup is free of bubbles, close bleeder valve securely. Bleed remaining cylinders in correct sequence and in same manner. Remove tool from combination valve.

Pressure Bleeder Installation (Typical). Scheme 5

BLEEDING PRESSURES

PRESSURE BLEEDING SPECIFICATIONS

BLEEDING SEQUENCE

BLEEDING SEQUENCE

DISC BRAKE - FRONT

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

DISC BRAKE - REAR

Caliper design automatically compensates for shoe wear; therefore, no brake adjustment service is required.

DRUM BRAKE SHOE

Note. Adjustment should only be required after relining or replacing shoes, or if length of adjusting screw is changed.

Scheme 6

1. Raise vehicle and remove wheels and drums. Check to make certain that parking brake cable and linkage, including levers on rear secondary shoes, are free. Measure brake drum inside diameter using inside caliper portion of tool (J-21177).
2. Adjust brake shoes to dimension obtained on outside caliper portion of tool (J-21177). Check brake fluid level in both master cylinder reservoirs. Add fluid if necessary. Adjust parking brake. (Scheme 6): Adjusting Brake Shoe Clearance (Through Backing Plate)
3. Install drums and wheel. Tighten wheel mounting nuts. Lower vehicle. Drive car alternately forward and backward, applying brakes moderately in each direction.

FRONT WHEEL BEARING

1. Install wheel on vehicle. Remove dust cap and cotter pin. Tighten spindle nut to 12 ft. lbs. (16 N.m) while spinning wheel by hand. Back off nut until just loose, then tighten by hand until snug.
2. Back off enough to insert new cotter pin (about 1/2 hex flat or 1/12 turn). Adjustment should provide .001-.005" (.03-.13 mm) end play. Install dust cap.

Check

Push rod height check is necessary if master cylinder and power unit were separated. Push rod is replaced with a new one. Push rod is transferred from one unit to another. If push rod misadjustment is diagnosed as braking problem.

Adjustment

1. Remove power unit from vehicle and place power head assembly in padded vise with front housing up. Remove front housing seal.
2. Insert push rod (flat end first) into piston rod retainer. Depress rod with 40-50 lbs. force to ensure it is seated. Place "Go/No-Go" gauge (J-22647) over push rod. Make sure gauge does not contact studs. (Scheme 7)
3. "Go" or short tab on gauge should just clear push rod; "No-Go" or long tab on gauge should contact push rod. If push rod is too long or too short, an adjustable push rod must be used. Adjust new push rod to correct height using "Go/No-Go" gauge.

Push Rod Gauging Method with "Go/No-Go" Gauge J-22647. Scheme 7

PARKING BRAKE (REAR DRUM BRAKE)

Note. When rear drum brakes are serviced, the parking brake linkage cable at the equalizer must always be readjusted to prevent possible burn out of rear brakes.

1. Lubricate parking brake linkage at equalizer and cable stud, and ensure free movement of cables. Depress parking brake pedal to approximately 1 1/2" from fully released position. Raise rear wheel. Hold brake cable from turning and tighten equalizer nut 1 turn at a time.
2. Check for brake drag after each turn by turning wheel forward. When light drag is felt on both wheels, release parking brake. No drag should be present at either wheel. After adjustment, apply approximately 125 lbs. of force to pedal or lever, travel should be as specified. See PARKING BRAKE ADJUSTMENT

PARKING BRAKE ADJUSTMENT

PARKING BRAKE (REAR DISC BRAKE)

With parking brake pedal fully released and rear wheels raised, hold brake cable stud to prevent turning and tighten equalizer nut until cable slack is removed. Make sure levers are on stops. If not, loosen equalizer nut until levers return against stops on caliper housing. After adjustment, pedal travel with 125 lbs. (170 N.m) force, should be as specified. See PARKING BRAKE ADJUSTMENT table

PARKING BRAKE ADJUSTMENT

HYDRO-BOOST

Note. Hydro-Boost cannot cause noisy brakes, fading brake pedal, or pulling brakes. If one of these condition exists, other components of brake system may be the cause.

Preliminary Checks

Make following checks and repairs, before performing any tests on Hydro-Boost system

1. Fluid levels in master cylinder & power steering pump.
2. Power steering pump drive belt.
3. Power steering hoses for leaks or kinks.
4. Air in brake fluid or power steering fluid.
5. Engine idle speed.
6. Steering pump pressure.

Note. If problem cannot be found in preliminary steps, make following tests. If unit is found to be operating properly, check areas of brake system that might cause condition. See HYDRO-BOOST TROUBLE SHOOTING .

Hydro-Boost Functional Test

1. Make all preliminary checks. Place transmission in neutral and stop engine. Apply brake several times to deplete accumulator reserve. Hold brake depressed with medium pressure (40 lbs.).
2. Start engine. Brake pedal should fall slightly then push back against foot. If no action if felt, booster system is not operating properly.

Accumulator Leakdown Test

1. Start engine, and charge accumulator by either applying brake with 100 lbs. pedal force or turning steering wheel lock to lock.
2. Turn off engine and wait 1 hour. There should be 1 reserve brake application with engine off.
3. If reserve system will not retain a charge for 1 hour, but functions normally immediately following charging, or if accumulator can be heard charging and discharging but will not hold a charge, accumulator valves are at fault, replace power piston/accumulator.

Note. If Hydro-Boost is not functioning, insure power steering system is operating normally before replacing Hydro-Boost unit.

Exploded View of Hydro-Boost. Scheme 8

HYDRO-BOOST SYSTEM FLOW CHARTS

Use the following flow charts to diagnose the Hydro-Boost brake system.

Procedure for Slow or Incomplete Pedal. Scheme 9

Procedure for Excessive Brake Pedal Effort - 1 of 2. Scheme 10

Procedure for Excessive Brake Pedal Effort - 2 of 2. Scheme 11

Lateral Runout

Adjust wheel bearings until all end play is eliminated. Attach a dial indicator to front suspension so pointer contacts face of rotor about 1 inch from edge. Set gauge to zero, then turn rotor through one complete revolution. (Scheme 12) Check gauge reading with specifications for maximum runout.

Checking Rotor Lateral Runout. Scheme 12

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 more than specified, refinish or replace rotor.

DISC PAD INSPECTION

Inspect linings every 6,000 miles or 12 months, or whenever wheels are removed. Check both ends of inboard and outboard linings for wear. Replace any that are worn to within .032" (.81 mm) of rivets on either end of lining.

DRUM BRAKE CLEANING

Clean all parts except the brake lining and the brake drums with brake cleaning solvent. To remove brake fluid contamination, clean all parts except the brake lining with denatured alcohol. Contaminated brake lining must be replaced.

DRUM BRAKE INSPECTION

1. Pull back the wheel cylinder dust boots and check for evidence of leakage. If evidence of leakage is noted, the cylinder should be disassembled, inspected and overhauled.
2. Polish the brake support plate ledges with fine emery cloth and inspect them for grooves that could restrict shoe movement. If grooves exist after polishing, the support plate must be replaced. Inspect lining wear pattern. If wear across the width of the lining is uneven, the drums should be checked for distortion, the shoes for correct positioning, and the support plate for distortion.
3. Inspect all springs for evidence of overheating and fractures. Self-adjusting cables should be inspected for kinks, fraying, or elongation of the eyelet. Inspect adjuster screws for freedom of rotation, and adjuster lever for wear and distortion.
4. Replace defective brake parts.

Removal

1. Without disconnecting hydraulic lines, remove master cylinder from power unit and position to one side. On Delco-Moraine models equipped with pipe distribution and switch mounting bolt, remove bolt before moving master cylinder away from power unit. CAUTION: Do not bend or kink hydraulic lines.
2. Disconnect vacuum hose from check valve on front of power unit. Disconnect push rod from brake pedal. CAUTION: Do not force push rod to the side when disconnecting.
3. Remove nuts mounting power unit to firewall and remove power unit.

Installation

Reverse removal procedure and check stop light and cruise control (if equipped) switch adjustments.

BRAKE BOOSTER - HYDRO-BOOST

Note. Before removing unit, discharge accumulator by making several brake applications until a hard pedal is obtained.

1. Remove nuts attaching master cylinder to booster. Move master cylinder aside without disconnecting brake fluid lines.
2. Disconnect pressure, steering gear and return lines from booster unit. Plug all lines and ports.
3. Remove retainer and washer from push rod and service brake pedal arm. Remove nuts securing booster to dash panel.
4. Remove booster unit by sliding push rod link out from engine side of dash panel.

1. Mount booster to dash panel by sliding push rod through hole in dash panel. Install attaching nuts loosely, tighten after completing steps inside vehicle.
2. Install master cylinder on booster unit, tighten nuts. Position push rod on service brake pedal arm and install washer and retainer. Remove plugs and attach fluid lines to booster unit.
3. Fill power steering reservoir. Disconnect 12-volt wire from injection pump and engage starter. Do not start vehicle. Check power steering fluid level, and top off, if necessary. Install 12-volt wire to injection pump and start engine; then cycle steering wheel twice.
4. Stop engine and discharge accumulator by depressing brake pedal 4 or 5 times. Check power steering level. Top off, if necessary. Start engine, cycle steering wheel once, and turn engine off. Check fluid level. If foaming occurs, wait 1 hour and recheck level.

DISC CALIPERS & PADS - FRONT

Note. Relining should be done in complete sets only.

1. Remove and discard 2/3 of brake fluid in master cylinder reservoir to prevent overflow during servicing. NOTE: Do not remove all fluid or disconnect brake line or it will be necessary to bleed system.
2. Raise vehicle and remove front wheels. Position a "C" clamp on caliper. Place solid side of clamp against inside of caliper and screw end of clamp against outboard shoe.
3. Tighten clamp until caliper moves away from vehicle. When caliper moves enough, push piston to bottom on its bore. This will allow shoes to back off from rotor surface.
4. Remove "C" clamp. Unbolt caliper from steering knuckle or support bracket.
5. Lift caliper off rotor and support with a wire so brake hose will not be damaged. Remove shoes and shoe support spring from cavity in piston. Remove sleeves from inboard ears of caliper and rubber bushings from all caliper ears.

1. Using silicone lubricant, coat and install new sleeves and rubber bushings in caliper ears. Attach shoe support spring to inboard shoe. Ensure that shoe is installed in caliper with wear indictor to rear of vehicle.
2. Position outboard shoe in caliper. Engage tab at bottom of shoe with caliper cutout and shoe ears with caliper ears at top of shoe. Place caliper over rotor, aligning caliper ears with mounting holes.
3. Start bolts or pins through inboard caliper ears and mounting bracket. Make sure bolts or pins pass under retaining ears of inboard shoes.
4. Push bolts or pins through caliper to engage hole in outboard shoe and ears of caliper. Thread bolts into mounting bracket and tighten.
5. Add brake fluid to fill master cylinder to within 1/8" of top. Pump brake pedal to seat shoes against rotor.
6. Use pliers to clinch upper ears of outboard shoe against caliper. (Scheme 13) Make sure ears are flat against caliper with no clearance.

Clinching Tabs on Outboard Shoe. Scheme 13

DISC CALIPERS & PADS - REAR

Note. Mark relationship of wheel to axle flange before removing wheels.

1. Remove and discard 2/3 of brake fluid in master cylinder reservoir. Raise vehicle on hoist. Remove wheel and tire. Replace 1 lug nut (flat side toward rotor) to retain rotor while removing caliper.
2. Loosen tension on parking brake cable at equalizer and disconnect brake cable from parking brake lever. Remove cable bracket from caliper. Remove return spring, lock nut, lever, lever seal and anti-friction washer. NOTE: Lever must be held in place while removing nut.
3. Clean any dirt from caliper in area of lever seal. Using a large "C" clamp, place solid end on lever stop and screw end on back of outer lining assembly. Turn clamp until piston bottoms in caliper. Remove "C" clamp. NOTE: Do not position "C" clamp on actuator screw.
4. Lubricate caliper housing surface under lever seal with silicon brake lubricant. Install new anti-friction washer. Lubricate new lever seal with silicone and install with sealing bead against housing. Install lever on actuator screw with lever pointing down.
5. Remove brake line from caliper. Plug opening to prevent fluid loss and keep dirt out of system. Remove caliper mounting bolts. Remove caliper with brake shoes. Inspect caliper assembly for damage, cuts, cracks or excessive leakage. Replace or repair as necessary. Remove and discard 2 caliper mounting sleeve and 4 bushings. Remove and discard piston check valve.

1. Install new piston check valve. Using silicone grease, install new bushings and sleeves. Place new inboard shoe on piston with "D" shaped tab fitting into indentation in piston. Install outboard shoe. NOTE: If piston requires rotation, use a spanner wrench (J-7624) to turn it.
2. Slide caliper over rotor and install mounting bolts under inboard shoe ears. Using new washers, install brake line. Pump brake pedal to seat lining against caliper. Using channel lock pliers, clinch upper ears of outboard shoe against caliper, making sure all ears are flat against caliper with no clearance. (Scheme 14)
3. Rotate lever toward front of vehicle and tighten nut. Rotate lever back against stop on caliper and install spring. Connect and adjust parking brake cable. After bleeding brake system, pump brake several times to adjust. Remove single lug nut used to retain rotor and install wheel.

Clinching Ears of Outboard Pad. Scheme 14

DISC ROTOR - FRONT

Raise and support vehicle. Remove wheel, then remove and support caliper. Remove grease cup, cotter pin and nut, then remove rotor. To install brake rotor, reverse removal procedure.

DISC ROTOR - REAR

Note. Mark relationship of wheel to axle flange before removing wheels.

Raise and support vehicle. Remove wheel and tire. Replace one lug nut (flat side toward rotor) to retain rotor while removing caliper. Remove caliper. See DISC CALIPERS & PADS - REAR under REMOVAL & INSTALLATION. To install reverse removal procedure.

DRUM BRAKE SHOE & LINING REPLACEMENT

Note. Mark position of springs and star adjusters as they are removed, for installation in original position.

1. Release parking brake and loosen parking brake cable at equalizer. If necessary, back off brake adjustment before removing brake drums. Remove return springs. Remove brake shoe hold down springs and cups. Lift up on parking brake actuator lever and remove actuator link. Remove actuator lever and return spring.
2. Separate brake shoes from wheel cylinder connecting links. Remove parking brake strut and spring. Disconnect parking brake cable. Remove brake shoes, spring and adjusting screw from backing plate. Detach spring and screw from brake shoes. Remove parking brake lever from secondary shoe.

Exploded View of Rear Drum Brake Assembly. Scheme 15

1. Lubricate fulcrum end of parking brake lever and attach to secondary shoe. Connect adjusting screw spring, then place screw in position. Ensure that star is aligned with adjusting hole. Lubricate surfaces where shoe and parking brake cable contact backing plate. Position shoes and insert into wheel cylinder links.
2. Connect cable to parking brake lever and install strut and spring between lever and primary shoe. Install actuator, actuator return spring and actuating link. Replace brake drums and wheels. Adjust parking brake and brake shoes. Check for proper operation of brakes before moving vehicle.

1. On power brake systems, disconnect switch wire (if equipped) and all hydraulic lines. Remove cylinder mounting nuts and remove cylinder.
2. On manual brake systems, disconnect negative battery cable, remove stop light switch and spring retainer (if required), disconnect switch wire (if equipped) and all hydraulic lines. Remove cylinder mounting nuts, slide cylinder forward to remove from pushrod and remove cylinder.

Bleeding

1. Master cylinder must be bled before bleeding entire system. Master cylinder bleeding may be done on vehicle. Preferred method is to bleed master cylinder on bench. If master cylinder has a bleed screw, bench method should still be used. When master cylinder is installed on car, use bleed screw as a final check for trapped air.
2. Place master cylinder level in a vise. Attach bleeding tubes to cylinder. Fill reservoirs with fluid so that ends of tubes are covered see scheme 14 Tubes attached to disc brake outlets must have residual pressure valves installed over ends. This will keep tubes from siphoning.
3. Stroke piston in bore with a wooden stick or dowel until bubbles no longer appear at ends of tubes. Remove tubes and plug the master cylinder disc brake outlets to keep fluid from draining.

1. To install, reverse removal procedure. Bleed master cylinder bleed screw first, if used, and then bleed remainder of system. See «HYDRAULIC BRAKE BLEEDING»(/chevrolet/camaro/ii-1970-1987/remont/mechanical-hydraulic/#disc-drum__hydraulic-brake-bleeding) section in this article.
2. Check master cylinder compensating ports by pumping brake pedal several times, ending with pedal held down. Remove master cylinder cover and slowly release pedal. Fluid should squirt up in each reservoir from the compensating ports.
3. If fluid does not squirt in each reservoir, port is plugged or pushrod is too long. Check for plugged port. If port is not plugged, adjust manual brake pushrod at clevis under dash. On power brakes, see «MASTER CYLINDER PUSH ROD»(/chevrolet/camaro/ii-1970-1987/remont/mechanical-hydraulic/#disc-drum) under ADJUSTMENT. CAUTION: DO NOT use wire to check ports. Wire may make a burr on port or damage cup.
4. Push rod should have slight amount of play when in relaxed position, so that both master cylinder pistons will return to stops when brakes are off.

REAR WHEEL CYLINDER

Two types of wheel cylinder retainers are used to hold the wheel cylinder to the backing plate. The first uses a ring type retainer, the second uses two retaining bolts.

Removal (Ring Type Retainer)

Remove dirt and foreign material from around wheel cylinder and pilot. Disconnect inlet tube line. Remove wheel cylinder retainer using Wheel Cylinder Retainer Ring Remover (J-29839) or 2 awls. Insert remover or awls into access slots between wheel cylinder pilot and retaining lock tabs. Bend both tabs away simultaneously until wheel cylinder is released. (Scheme 16)

Scheme 16

To install, hold cylinder on backing plate by inserting a wood block between wheel cylinder and axle flange. Install a new retaining spring over wheel cylinder, lining up retainer tabs with cylinder tab grooves. Drive retainer into position using 1 1/8" socket and a 10" extension. Retainer is in position when tabs are snapped under retainer abutment.

Removal (Bolt Type Retainer)

Disconnect inlet tube line and remove 2 screws holding wheel cylinder to backing plate. Remove wheel cylinder.

To install, replace wheel cylinder in position and install screws. Connect inlet tube line.

Disassembly

1. Disconnect master cylinder from power unit and power unit from vehicle. Scribe power unit housings for reassembly reference. Remove front housing seal and piston rod.
2. Attach power unit front housing to holding fixture base (J-22805) and clamp base in vise with power section up. Remove lock nut and push rod clevis. Remove rear housing mounting bracket. Remove dust boot retainer, boot, silencer and air filter.
3. Partially straighten the 4 deepest tabs on rear housing. Place a spanner wrench (J-9504) onto studs of rear housing. Press down and turn rear housing clockwise to separate 2 housings. Carefully remove rear housing. CAUTION: Housings are under internal spring pressure.
4. Remove air filter from plate extension. Remove diaphragm from plate. Do not damage diaphragm or plate. Hold diaphragm plate so push rod is horizontal. Depress and rotate rod until air valve lock falls out. Remove reaction disc. CAUTION: Remove seal only if new one is available. Do not reuse old seal once it has been removed.
5. Remove rear housing bearing seal. Remove vacuum check valve and grommet. Remove front housing and holding fixture from vise and remove front housing.

Cleaning & Inspection

Use only denatured alcohol or clean brake fluid to clean parts. Use clean dry air to blow out all passages, orifices, and valve holes. Blow dry all parts. Polish any areas with slight rust, on inside of housing, with crocus cloth. Replace any rubber parts that are cut, nicked, or distorted.

Reassembly

1. Install vacuum check valve grommet (beveled edge on inside) after dipping part in denatured alcohol.
2. Install front housing on a holding fixture (J-22805), and clamp fixture in a vise.
3. Install new rear housing seal using seal installer tool (J-22677), tool bottoms on housing when seal is in place.
4. Assemble diaphragm plate assembly as follows: Lubricate outer diameter of diaphragm plate, extension, valve, plunger bearing surfaces and edge of poppet valve. Install valve and rod into diaphragm plate extension. Depress pushrod and install lock. Install rolling diaphragm in diaphragm plate groove. Lubricate and install reaction disc. Use master cylinder push rod to seat disc in diaphragm bore. NOTE: If disc is not fully seated, push rod height will be incorrect.
5. Lubricate inside of bearing seal and diaphragm contact surface of rear shell. Install diaphragm plate assembly in rear housing. Install air filter and retainer into diaphragm plate extension.
6. Complete assembly as follows: Place spanner wrench on rear housing. Press wrench down and turn rear housing counterclockwise to lock housings together. Make sure scribe marks align. Bend tabs back into place so housings will not come apart. If any tabs are broken, replace housing.
7. Install air silencers, push rod boot and retainer. On clevis type push rods, install lock nut and clevis. Lubricate piston rod (except rounded end). Install rod into center bore until seated against reaction disc. Install front housing seal in same manner as rear seal. Install master cylinder and bleed system if necessary.

1. Scribe marks on housings for reassembly reference and remove boot, front housing seal, vacuum check valve and grommet.
2. Attach power unit front housing to holding fixture base (J-22805-1) and clamp base in vise with power section up.
3. Place a spanner wrench (J-9504) on studs of rear housing. Press down and turn counterclockwise to unlock housings. NOTE: Do not put pressure on plastic power piston extension.
4. Remove power piston bearing, return spring and power piston group. Remove piston rod and reaction retainer. CAUTION: Use care not to damage power piston assembly when removing reaction disc. Reaction disc must be replaced.
5. Use awl, ice pick or similar tool to remove filter. Remove reaction disc and reaction piston.
6. Grasp assembly at outside edge of diaphragm support and diaphragm. Hold pushrod down against a hard surface. Use a slight force or impact to dislodge diaphragm retainer.

Note. Do not disassemble power pushrod assembly.

Exploded View of Typical Delco-Moraine 1-Diaphragm Booster. Scheme 17

Clean all metal, plastic, and rubber parts in denatured alcohol. Blow out all passages, orifices, and valve holes with clean, dry air. Air dry all parts. Slight rust on inside of housings can be polished with crocus or emery cloth. There should be no nicks, cuts, or abnormalities of any rubber part. If in doubt about its condition, replace the part.

1. Lubricate inside diameter of diaphragm lip with silicon lubricant and fit in diaphragm support.
2. Install diaphragm and support over power piston and pushrod assembly, support side first. Install new diaphragm retainer and seat using seating tool (J-28458) and a plastic hammer.
3. Install filter, reaction retainer, and piston rod. Attach holding fixture to front housing and place in vise. Install power piston return spring with White end to front housing.
4. Insert power piston assembly pushrod end through rear housing and place on front housing and return spring. Align scribe marks with spanner on studs of rear housing. Press down and turn clockwise to lock 2 housings. NOTE: Assembly can be aided by connecting a vacuum source to booster.
5. Stake 2 housing tabs into sockets with screwdriver. Stake at 2 tabs 180° apart. Lubricate inside and outside diameters of grommet and front housing seal and install seal and grommet. Vacuum check valve and boot.

1. Remove pushrod boot, silencer, front housing seal, grommet and vacuum check valve.
2. Scribe a mark on front and rear housings for reassembly reference. Attach front housing to holding fixture (J-22805-01).
3. Place spanner (J-9504) over rear housing studs, press down and turn counter-clockwise to unlock housings.
4. Remove power piston group, power piston return spring, and power piston bearing. Remove piston rod, reaction retainer and power head silencer.
5. Grasp assembly at outside edge of divider and diaphragms. Hold with pushrod down against a hard surface. Use a slight force or impact to dislodge diaphragm retainer.
6. Remove primary diaphragm, primary support plate, secondary power piston bearing, housing divider, secondary support plate and diaphragm and power piston assembly.

Clean all plastic, metal and rubber parts in denatured alcohol. Blow out all passages, orifices and valve holes. Air dry all parts. Slight rust on housing may be cleaned with crocus or emery cloth. Do not reinstall any rubber parts with cuts, nicks or distor- tion. If in doubt, replace the part.

Note. Prior to installation of rubber, plastic, and metal friction parts, lubricate with silicone lube.

Scheme 18

Scheme 19

1. Place power piston on bench with push rod end up. Install assembly cone J-28458 over push rod end of piston. Lubricate inside diameter of secondary diaphragm with silicon lubricant and fit in secondary support plate.
2. Install secondary diaphragm and support plate over power piston and push down until it bottoms. Lubricate inside diameter of secondary power piston bearing. Install bearing in housing divider with flat surface of bearing on the same side as 6 raised lugs on divider. (Scheme 18): Exploded View of Delco-Moraine Tandem Diaphragm Booster (Scheme 19): Installing Secondary Diaphragm & Support Plate
3. Hold divider so that formed flange faces up. Press divider down over assembly cone and onto power piston to rest against secondary diaphragm. Lubricate inside diameter of primary diaphragm and install in primary support plate. Remove assembly cone from power piston, place primary support plate and diaphragm assembly over power piston and push down until it bottoms.
4. Place diaphragm retainer over power piston and onto diaphragm. Install assembly cone (J-28458) over power piston onto diaphragm retainer and strike with hammer until retainer is locked on neck of power piston. Remove assembly cone.
5. Install reaction retainer, piston rod and power head silencer. Place primary power piston bearing in rear housing center hole. Lubricate with silicone lubricant on inner diameter. Attach power piston assembly to rear housing.
6. Install power piston return spring over reaction retainer and lower rear housing onto front housing. Align scribe marks and press down with spanner and turn clockwise to lock 2 housings. Stake 2 housing tabs into sockets at 2 new locations 180° apart.
7. Lubricate inside and outside diameters of grommet and front housing seal. Install seal, grommet, vacuum check valve, silencer and push rod boot.

BRAKE BOOSTER - DELCO HYDRO-BOOST

1. Secure booster mounting bracket in vise with pedal rod pointing down. Pump pedal rod until accumulator pressure is depleted. WARNING: Accumulator contains compressed gas and injury may result if the following is not heeded: Wear safety glasses. Do not apply heat to accumulator. Do not attempt to repair accumu- lator. Replace with new assembly. Before disposing of an inoperative accumulator, drill a 1/8" hole through the end of can, opposite "O" ring. DO NOT drill through piston end.
2. Using special socket (J-25085), loosen Torx-head bolts securing front housing to rear housing. While holding front housing, remove Torx-head bolts. Have pan ready to catch and discard leaking fluid.
3. Use care when handling front housing as the accumulator contains a high rate spring in compression. Lift off front housing leaving spool valve and power piston/accumulator assembly attached to rear housing.
4. Remove output rod and piston return spring from power piston/accumulator assembly. Remove spool valve spring from valve. Remove output rod retainer assembly from front housing. Remove spool valve by rotating it out of lever arm. Remove and discard large "figure eight" seal from rear housing. Remove and discard power piston seal from bore.
5. Inspect spool valve and power piston for wear or scratches. Replace if necessary.
6. Remove power piston by cutting end of connecting pin. Push out pin with a small punch and remove piston. Clean all parts in power steering fluid.

Note. Whenever booster is disassembled all seals and damaged tube inserts should be replaced. All accumulator valve components must be replaced if any are lost or damaged. If the spool valve bore is damaged, the entire booster should be replaced as an assembly.

1. Position piston bracket into yoke of lever and install new pin through hole. Use a punch to mushroom end of pin. Make sure lever is free to move with no binding.
2. Install new seal in rear housing groove and new power piston seal in front housing. Insert spool valve spring and spool valve assembly into bore of front housing.
3. Pull up on power piston and extend lever to accept sleeve on spool valve. While holding lever extended, bring front housing with spool valve directly over rear housing and slide lever pins into slot in sleeve.
4. To install rear housing to front housing center power piston/accumulator in bore. Before housings contact, install seal protector through piston bore until seated on piston. Push housings together and remove seal protector. Tighten Torx bolts to 20 ft. lbs. (27 N.m).
5. Install output rod, spring and a new spring retainer. Using a 7/8" deep socket, secure new output rod retainer in place.

1. Clean exterior of caliper with denatured alcohol and place on a clean work surface. Remove brake shoe and discard copper gasket. Drain fluid from caliper. WARNING: DO NOT attempt to catch or protect piston with fingers while applying compressed air. Injury may result.
2. Using clean shop towels to pad interior of caliper, apply just enough clean compressed air to caliper inlet so piston will ease out of bore.
3. Using a screwdriver, pry boot out of caliper. Pry piston and seal from caliper using a piece of wood or plastic. DO NOT use a metal tool as bore may be damaged requiring caliper replacement. Remove bleeder valve from caliper.

1. Replace boot, piston seal, rubber bushings and sleeves each time caliper is overhauled.
2. Clean all parts in denatured alcohol. Dry parts using clean dry compressed air. Lubricated shop air will ruin rubber parts upon contact at reassembly.
3. Check mounting bolts for corrosion, breaks in plating or other damage. Replace bolts if damaged in any way. DO NOT attempt to wire brush or clean them.
4. Check outside diameter of piston for scoring, nicks, corrosion, or worn and damaged plating. If surface defects are visible, replace piston. DO NOT attempt to refinish with abrasives.
5. Check piston bore in caliper for scratches or other damage. Minor scratches or corrosion may be polished clean with crocus or emery cloth. Thoroughly clean bore after polishing. Replace caliper if corrosion is not easily cleaned.

1. Lubricate bore in caliper and new piston seal with clean brake fluid. Position seal in caliper bore groove. Lubricate piston with clean brake fluid. Assemble new boot into groove in piston with fold facing open end of piston.
2. Insert piston into caliper bore using care not to unseat seal. Do not force piston to bottom of bore. Position outer diameter of boot in caliper counterbore. Seat boot using dust boot installer.
3. Check boot installation to make sure retaining ring moulded into boot is not bent and that boot is installed completely below caliper face. Install brake hose, using a new copper gasket.

Note. After caliper has been overhauled and installed, it must be bled.

1. With caliper held in a vise, remove 2 mounting sleeves and 4 bushings from caliper and discard. Remove brake shoes and lever return spring. Using a shop towel to catch piston and brake fluid, rotate lever back and forth to move piston out of caliper housing. NOTE: If piston will not move out of housing, remove lock nut, lever, seal and anti-friction washer. Use a wrench to turn activator screw until piston pops out of housing.
2. Remove piston seal assembly and balance spring. Remove lock nut, lever, seal and anti-friction washer. Push screw out of housing and remove piston seal, copper washer and boot.
3. Thoroughly clean all parts with denatured alcohol. Inspect caliper bore for scoring, nicks, corrosion or wear. Use crocus cloth to polish any light corrosion. Replace if necessary. Check outer diameter of piston for nicks, scoring or damaged plating. If surface defects are visible, replace piston.

Scheme 20

1. Install bleeder screw and tighten. Install fitting and bolt using new copper washers. Lubricate new piston seal with brake fluid and install into caliper bore groove.
2. Fit boot on piston with inside lip of boot in piston groove and boot fold toward end of piston that contacts inboard brake shoe. Install new thrust washer and seal on actuator screw.
3. Lube actuator screw with brake fluid and install in piston. Fit balance spring into piston and start piston assembly into caliper housing. NOTE: Caliper housing and activator screws must be installed on the same side of the car as they were removed from. If parts are on the wrong side parking brake will not work. (Scheme 20): Exploded View of Delco-Moraine Single Piston Rear Caliper
4. Using piston installer tool (J-23072) screw piston all the way back into housing. Ensure that piston is straight or screw may damage seal as it passes through. Before removing tool, install lever away from stop, rotate forward and hold while tightening nut.
5. Remove tool (J-23072), rotate lever back to stop and install return spring (Red-right side, Black-left side). Using boot installer tool (J-28678), drive boot in until seal bottoms in housing. Install lining and caliper. See «DISC CALIPERS & PADS - REAR»(/chevrolet/camaro/ii-1970-1987/remont/mechanical-hydraulic/#disc-drum__disc-calipers-pads-rear) under REMOVAL & INSTALLATION.

See DRUM BRAKE SHOE & LINING REPLACEMENT under REMOVAL & INSTALLATION.

1. Drain all brake fluid from master cylinder and clean outside of master cylinder before disassembly. Remove reservoir cover and gasket. On aluminum master cylinders (with removable reservoirs) place a pry bar between master cylinder body and reservoir. Pry up until reservoir can be removed.
2. On all master cylinders, place cylinder in a vise. Depress piston and remove stop screw, if equipped. Remove lock ring from groove in end of bore or retainer and screw. Remove rear (primary) piston assembly. CAUTION: Do not disassemble rear piston assembly or change adjustment of screw.
3. Remove front (secondary) piston with air pressure. If air pressure does not work, use wire hook to pull piston out end of cylinder. Remove front piston spring if it did not come out with piston. Remove splash seal and retainer outside rear of cylinder, if they are used.
4. Remove tube seats to gain access to check valves. If removal kit is not available, use one of the following methods. Thread a short screw into seat and then pry screw and seat out with a screwdriver.
5. Another method is to drill a 13/64" hole through each seat. Then tap hole with a 1/4-20 tap. Screw a tubing nut into outlet. Then insert a 1/4-20 machine screw (with washer) through nut and into tube seat. Hold screw from turning. Unscrew the tubing nut to remove seat. Remove check valve and spring from drum brake outlet.

Typical Delco-Moraine Master Cylinder. Scheme 21

Typical Bendix Master Cylinder. Scheme 22

Inspection

On cast iron master cylinders, inspect cylinder bore for scoring or corrosion. Staining on cast iron master cylinders which has not pitted or roughened the surface can be removed with crocus cloth. Move cloth in circular manner. Never polish cylinder with lengthwise strokes. If cylinder is scored, corroded or pitted, replacement is recommended.

On aluminum master cylinders, the body of the master cylinder is anodized. Some signs of bore wear on the anodized surface is normal. This will appear as lighter areas in the anodized surface. If cylinder bore is heavily worn or scored, replace master cylinder.

Scheme 23

Scheme 24

1. Put check valve spring in drum brake outlet. CAUTION: Check valve in disc brake outlet will cause disc brakes to lock up.
2. Put check valve on top of spring and insert tube seat in outlet against valve. Using a spare flare nut, screw nut into outlet to bottom tube seat. Remove nut and inspect for burrs or shavings caused by installing seat. NOTE: Before assembly, dip all component parts in clean brake fluid. Assembling seals dry can damage them. CAUTION: On aluminum master cylinders, DO NOT polish cylinder bore with anything abrasive.
3. Install new secondary cups on rear of front (secondary) piston. Place cup lips facing away from each other. Some front pistons use a cup in rear grooves and an "O" ring in second groove from rear. Place cup so lip faces forward and back of cup is against protector washer. NOTE: Protector washer may be permanently attached to cup. (Scheme 23): Aluminum Body Master Cylinder Type 1 (Scheme 24): Aluminum Body Master Cylinder Type 2
4. Coat bore of cylinder and all cups with brake fluid. Place spring retainer on end of front spring. Place spring on end of front piston so that retainer is seated inside cup. Hold open end of master cylinder down. Push front spring and piston up into bore until spring seats against end of cylinder.
5. Hold master cylinder with open end up. Insert rear piston assembly with spring end going in first. Install lock ring in groove, or screw and retainer if used. Push rear piston into bore. Install stop screw and "O" ring if used. NOTE: Stop screw is a special screw. DO NOT use any other type as a substitute.
6. Install housing-to-reservoir grommets. Install reservoirs to housing, seating against grommets with a rocking motion. Install master cylinder cover and gasket. Place beaded side of gasket against master cylinder.
7. On manual brake systems, assemble pushrod through retainer, if used. Push retainer over end of master cylinder. Install a new boot over pushrod and press boot down over pushrod retainer.

With wheel cylinder removed from vehicle, remove rubber boots from ends of cylinder. Remove piston, piston return spring, cups and bleeder screw. Inspect cylinder bore for scoring or corrosion. Replace wheel cylinder if corrosion cannot be removed with crocus cloth or if bore is scored. Rinse with brake fluid.

Exploded View of Wheel Cylinder Assembly. Scheme 25

Install bleeder screw. Lubricate cylinder bore with brake fluid and install piston cup in 1 end of cylinder with lip toward center and install piston with flat side toward cup. Install rubber boot into end of cylinder. Install spring and expander assembly into opposite end. Install remaining cup, piston and rubber boot.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

WHEEL LUG NUT TORQUE SPECIFICATIONS

DISC BRAKE SPECIFICATIONS

DISC BRAKE ROTOR SPECIFICATIONS

DRUM BRAKE SPECIFICATIONS

DRUM BRAKE SPECIFICATIONS

See also:
• BLEEDING SEQUENCE
• HYDRO-BOOST TROUBLE SHOOTING
• DISC CALIPERS & PADS - REAR
• HYDRAULIC BRAKE BLEEDING