Disc & Drum GMC S15 Pickup

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. The vacuum power cylinder and the dual master cylinder. Vacuum power cylinder contains power piston assembly, which houses 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.

DISC BRAKES

Delco floating caliper disc brake assembly uses a single piston caliper. The caliper is mounted to an anchor plate which is bolted to the steering knuckle. The caliper assembly floats through 4 rubber bushings on 2 steel guide pins.

The pins are threaded into caliper anchor plate. When brakes are applied, hydraulic pressure is passed to caliper piston. This force pushes inner brake pad against inner rotor braking surface.

Pressure then moves caliper inward on guide pins, thus forcing outer disc pad against outer rotor braking surface. When brakes are released, pressure is removed from cylinder. Rotor runout moves piston back off of rotor to maintain sufficient rotor-to-pad clearance.

Exploded View of Floating Caliper Assembly. Scheme 2

DRUM BRAKE

Delco single anchor, duo-servo type brake assemblies are used on the rear of all models. The assemblies consist of a support plate, 2 brake shoes, return springs, automatic adjuster components and a duo-servo wheel cylinder.

Automatic adjusters consist of a connecting link, override lever, override spring, return spring, actuating lever and an adjusting screw. Normal adjustment is accomplished through movement of actuating lever and secondary shoe during application of brakes when vehicle is operated in reverse.

PRESSURE DIFFERENTIAL BRAKE WARNING SWITCH

This switch is used to warn vehicle operator that one of the hydraulic systems has failed. When hydraulic pressure is equal in both front and rear systems, switch piston remains centered and does not contact terminal in switch

If brake system fails, hydraulic pressure moves piston toward failed side. Shoulder of piston then contacts switch terminal to provide for brake warning light.

PROPORTIONING VALVE

Valve operates by restricting, at a given ratio, hydraulic pressure to rear brakes when system hydraulic pressure reaches a certain point. This improves front-to-rear brake balance at high speed braking, when a percentage of rear weight is transferred to front wheels.

Valve reduces rear brake pressure, and delays rear wheel skid. On light brake application, valve allows full hydraulic pressure to rear brakes.

METERING VALVE

This valve holds off pressure to front disc brakes to allow rear drum brake shoes to overcome return spring pressure and make contact with rear drums. This prevents locking front brakes on slippery or icy surfaces under light braking conditions. Valve has no effect on front brake pressure during hard braking conditions.

Delco Quick Take-Up

The Delco Quick Take-Up master cylinder is a 2 piece unit with cast master cylinder body and plastic fluid reservoir. It is designed for use with systems utilizing low drag calipers.

This master cylinder includes a quick take-up valve. This valve delivers a large volume of fluid, at low pressure, upon initial application of brakes. The fluid quickly displaces retracted calipers, placing brake linings in contact with brake rotors and drums.

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 been run dry. Bleed brakes with pressure bleeding equipment or by manually pumping brake pedal while using bleeder tubes.

HYDRAULIC CONTROL VALVES

On disc brake equipped vehicles, metering section of hydraulic control valve must be deactivated before bleeding to permit fluid to flow to front brakes. This is especially important when pressure bleeding.

Use Combination Valve Depressor (J-23709), If tool is not available, hold valve open by hand. DO NOT use "C" clamp or other non-yielding device to hold valve open.

PRESSURE TANK BLEEDING

1. Clean master cylinder cap and surrounding area. Remove cap. Deactivate hydraulic control valve. With pressure tank at least 1/2 full, connect to master cylinder with adapters. Attach bleeder hose to first bleeder valve to be serviced. See BLEEDING SEQUENCE table.
2. Place other end of hose in clean glass jar partially filled with clean brake fluid so end of hose is submerged in fluid. Open release valve on pressure bleeder. Follow equipment manufacturers pressure instructions unless noted below.
3. Unscrew bleeder valve 3/4-1 turn noting fluid flow. When fluid flowing from cylinder to jar is free of bubbles, close bleeder valve securely. Bleed remaining cylinders in correct sequence and in the same manner. Remove tool from control valve.

PRESSURE BLEEDER SETTINGS

MANUAL BLEEDING

Note. When bleeding disc brakes, air may tend to cling to caliper walls. Lightly tap caliper, while bleeding, to aid in removal of air.

1. Fill master cylinder. Install bleeder hose to first bleeder valve to be serviced. See BLEEDING SEQUENCE table. Submerge other end of hose in clean glass jar partially filled with clean brake fluid.
2. Open bleeder valve 3/4-1 turn. Depress brake pedal slowly through full travel. Close bleeder valve and release pedal. Repeat procedure until flow of fluid shows no signs of air bubbles.

Wheel Cylinder Bleeding Procedure Bleeder valve must be closed when brake pedal is released. Scheme 3

BLEEDING SEQUENCE

Before bleeding system, exhaust all vacuum from power unit by depressing brake pedal several times. Bleed master cylinder if equipped with bleeder screws. Bleed slave cylinder on vehicles equipped with remote mount power assist units. Bleed wheel cylinders and calipers in sequence. See BLEEDING SEQUENCE table.

BLEEDING SEQUENCE

DISC BRAKE

Pad wear is automatically compensated for by piston moving outward in cylinder bore. No disc pad adjustment in service is required.

Inspect condition of disc pads whenever wheels are removed. If any disc pad is worn to within 1/32" (.8 mm) of rivet heads, replace all disc pad sets on that axle.

DRUM BRAKE SHOE

1. Knock out lanced area in brake drum with a punch. If drum is installed, it must be removed and all metal removed from brake area.
2. Turn adjusting screw, through hole, until brake shoes expand and brake drums can just be turned by hand. The drag should be equal at all wheels.
3. Back off adjusting screw 30 notches at each wheel. If drum still drags, back off an additional 1 or 2 notches. Install hole cover in drum.

Exploded View of Single Anchor Brake Assembly. Scheme 4

FRONT WHEEL BEARING - 2WD

Tighten bearing nut to 12 ft. lbs. (16 N.m) on while spinning wheel forward. Back off nut until it is just loose. Hand-tighten nut, then loosen slightly (no more than 1/12 turn) until cotter pin can be inserted. End play should be .001-.005" (.03-.13 mm).

MASTER CYLINDER PUSH ROD

Note. On some models, production push rod is not adjustable. If production rod is reused, gauging is to check proper assembly. If adjustable service push rod is used to replace production rod, use procedure to set to correct rod length.

Scheme 5

1. Place power unit in a vise with front housing up. Remove front seal to ensure all vacuum is released from unit. Place master cylinder rod, flat end first, in piston rod retainer. Press down on rod with 50 lbs. (23 kg) pressure to make sure rod is seated. (Scheme 5): Checking Push Rod Height With Gauge (J-22647)
2. Place gauge (J-22647) over piston rod so it can be moved from left to right without contacting studs. The center section of gauge has 2 levels.
3. The piston rod should always contact the lower level and never contact the highest level. If the push rod does not contact gauge correctly, an adjustable push rod must be obtained.
4. Adjust locking screw on rod to obtain correct clearance with gauge. Apply silicone lubricant on the inside diameter of front housing seal and place seal in position in housing depression.

PARKING BRAKE

1. With service brakes correctly adjusted, raise vehicle until both rear wheels are off ground. Loosen equalizer adjusting nut. Apply parking brake 2 notches on 2WD models, (4 notches on 4WD models), from fully released position.
2. Tighten adjusting nut until a slight drag is felt when wheels are rotated forward. Tighten lock nut. Release parking brake and wheels should rotate forward freely. Lower vehicle.

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

Pad wear is automatically compensated for by piston moving outward in cylinder bore. No disc pad adjustment is required. Inspect condition of disc pads whenever wheels are removed. If any pad is worn to within 1/32" (.8 mm) of rivet heads, replace all pad sets on axle.

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.

BRAKE BOOSTER

Note. Power brake unit can be removed without removing master cylinder or disconnecting brake lines.

Removal

1. Disconnect vacuum line from check valve or power unit. Remove nuts securing master cylinder to power unit.
2. Pull master cylinder forward away from unit. Disconnect brake pedal from push rod. Remove power unit-to-firewall bolts and remove unit.

Installation

To install, reverse removal procedures. If equipped with adjustable push rod, adjust before installation. See MASTER CYLINDER PUSH ROD under ADJUSTMENT.

1. Remove 2/3 of brake fluid from front reservoir in master cylinder. Raise vehicle and support with safety stands. Remove wheel assembly. Place a large "C" clamp on caliper so that solid side of clamp rests against metal part of outer disc pad.
2. Tighten "C" clamp until caliper moves away from vehicle far enough to push piston to bottom of bore. Remove "C" clamp. Do not disconnect brake line to caliper. Remove 2 mounting bolts which retain caliper to support bracket.
3. Lift caliper off rotor and remove inner disc pad. Pry out outer disc pad. Place caliper on front suspension arm so that caliper weight is not supported by brake hose or remove caliper as necessary.
4. Remove shoe support spring from cavity in piston. Remove sleeves from inner ear in caliper. Remove rubber bushings from grooves in each of 4 caliper ears.

1. Install new rubber bushings in 4 caliper ears. Install sleeves in bushings with installer tool (J-22835). Position sleeves so that end toward disc pad is flush with machined surface of ear.
2. Install shoe support spring on inner disc pad. Place single tang end of spring over notch in center edge of pad. Now press 2 tangs at spring end of inner disc pad over bottom edge of pad.
3. Place inner disc pad in caliper (with spring attached) so that the ear end of disc pad is down and the bottom end is up. Install at an angle so that the spring rests on the inside diameter of piston.
4. Press down on both ends of disc pad until pad is in a flat position, resting on piston. Be sure to install inner brake pads on the correct side. Wear sensor will be toward the rear of the caliper when correctly installed.
5. Place outer disc pad in caliper with ears of pad over caliper ears. Tab at bottom of pad should be engaged in caliper cut-out. Note left and right disc pads. Place caliper over rotor, line up caliper ears with holes in the mounting bracket.
6. With caliper in place, make sure brake hose is not twisted. Start bolts through sleeves in inner caliper ears and mounting bracket. Make sure that bolts pass under retaining ears in inner disc pad.
7. Push bolts through holes in outer disc pads and caliper ears. Thread bolts into mounting bracket and tighten to 35 ft. lbs. (48 N.m). Fill master cylinder with new brake fluid.
8. If caliper hose was disconnected, bleed brake system. Pump brake pedal several times to seat disc pads against rotor. Clinch upper ears of outer disc pad with channel lock pliers, placing 1 jaw on top of upper ear and other jaw on bottom of disc pad, in notch.
9. After clinching, ears should be flat against caliper housing with no radial clearance. If clearance exists, repeat procedure.

Removal (2WD Models)

1. Raise vehicle and support with safety stands. Remove brake caliper (do not disconnect brake line).
2. Remove grease cover from end of hub. Remove cotter pin nut, washer, and outer bearing. Remove rotor and hub assembly.

Install rotor and hub assembly on spindle. Install outer bearing, washer, and nut. Adjust wheel bearings. See Wheel Bearing Adjustment in appropriate SUSPENSION article in the SUSPENSION Section.

Removal & Installation (4WD "S" Series Models)

Raise vehicle and support with safety stands. Remove Wheel. Remove brake caliper. Do not disconnect brake hose. Remove rotor.

To install, reverse removal procedure.

1. Raise vehicle and support with safety stands. Remove wheel assembly and brake drum. It may be necessary to back off brake shoe adjustment before removing drum. Unlock primary and secondary shoe springs. Remove shoe hold down springs. NOTE: On some vehicles, it may be necessary to remove axle shafts to remove hub and drum.
2. Lift up on actuator, unhook actuating link from anchor pin and remove link. Spread shoes enough to clear wheel cylinder links. Remove parking brake strut and spring. Disconnect cable from lever. Remove brake shoes.

1. Lubricate fulcrum end of parking brake lever with brake lubricant. Attach lever to secondary shoe. Make sure lever moves free. Connect brake shoes together with adjuster spring.
2. Place adjuster screw in position. Make sure spring does not contact starwheel portion of adjusting screw. Right hand thread adjusting screw should be on left side.
3. Make sure starwheel lines up with hole in backing plate. Apply a thin coating of brake lubricant to contact surface on backing plate. Position brake shoes on backing plate.
4. Primary shoe (short lining) is to front. Connect cable to parking brake lever. Install strut between shoes. Install actuator, return spring and actuator link. Install shoe hold down springs.
5. Install both primary and secondary shoe springs. Measure inside diameter of brake drum with measuring gauge (J-21177). Expand brake shoes to dimension obtained on outside caliper portion of tool.
6. Install brake drum and wheel assembly. Bleed system if any portion of hydraulic system was opened. Check fluid level in master cylinder and add as necessary.

1. Disconnect front and rear hydraulic brake lines at master cylinder, and cover ends to prevent entry of foreign matter.
2. On vehicles without power assist units, disconnect brake pedal push rod at brake pedal. Remove master cylinder retaining bolts, and remove cylinder assembly from vehicle.

1. Position master cylinder on vehicle and install cylinder retaining bolts. Connect front and rear hydraulic brake lines to cylinder.
2. Connect brake pedal push rod, if removed. Fill reservoir with clean brake fluid, and bleed hydraulic system. See HYDRAULIC BRAKE BLEEDING.

1. Raise and support vehicle. Remove wheels and brake drums. Loosen differential cover plate and drain lubricant from axle. Remove cover plate.
2. Remove pinion shaft lock bolt. (Scheme 6) Remove pinion shaft that goes between pinion gears. Push axle shaft inward and remove "C" lock from end of axle shaft. Remove axle shaft.
3. Pry seal from axle housing. Using Slide Hammer (J-2619-01) and Bearing Puller (J-22813-01), remove bearing from axle housing.

Scheme 6

1. Using Handle (J-8092) and Bearing Installer (J-23765), install bearing in axle housing until bearing installer bottoms against shoulder of axle housing. Lubricate bearing with axle lubricant.
2. Using Seal Installer (J-23771), install seal until it is even with surface of axle housing. Install axle shaft and "C" lock. Pull axle shaft outward to ensure "C" lock seats in side gear.
3. Install NEW pinion shaft lock bolt. Tighten lock bolt to 25 ft. lbs. (34 N.m). Install differential cover and new gasket. Refill drive axle with lubricant.

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 7)

Scheme 7

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. 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 reaction disc. Remove reaction piston. Grasp assembly at outside edge of diaphragm support and diaphragm.
6. Hold pushrod down against a hard surface. Use a slight force or impact to dislodge diaphragm retainer.

Typical Delco-Moraine Single Diaphragm Power Brake Unit Do not disassemble power push rod assembly. Scheme 8

1. 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.
2. Slight rust on inside of housings can be polished with crocus or emery cloth. There should not be any nicks or cuts on rubber part. Replace any damaged part.

Reassembly

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

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

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

Exploded View of Delco-Moraine Tandem Power Cylinder. Scheme 9

Exploded View of Delco-Moraine Tandem Power Piston Assembly. Scheme 10

Note. Lubricate rubber, plastic, and metal friction parts with silicone lube before assembly.

Scheme 11

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 silicone lubricant and fit in secondary support plate.
2. Install secondary diaphragm and support plate over power piston and push down until it bottoms. (Scheme 11) Lubricate inside diameter of secondary power piston bearing and install in housing divider with flat surface of bearing on the same side as 6 raised lugs on divider. (Scheme 11): Installing Secondary Diaphragm and Support Plate Use installer cone (J-28458).
3. Hold divider so that formed over 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.
4. Remove assembly cone from power piston. Place primary support plate and diaphragm assembly over power piston and push down until it bottoms. Place diaphragm retainer over power piston and onto diaphragm.
5. 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.
6. 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.
7. Attach front housing to holding fixture and place fixture in vise. Install power piston assembly to rear housing. Install power piston return spring over reaction retainer and lower rear housing onto front housing.
8. Align scribe marks and press down on spanner wrench (J-9504), turning clockwise to lock housings. Stake 2 housing tabs into sockets at 2 locations 180° apart.
9. Lubricate inside and outside diameters of grommet and front housing seal. Install seal, grommet, vacuum check valve, silencer, and push rod boot.

1. Clean exterior of caliper with denatured alcohol and place on clean work surface. Remove brake hose, discarding copper gasket. Drain brake fluid from caliper.
2. Use clean shop towels to pad interior of caliper and apply compressed air at caliper inlet to remove piston. Use just enough pressure to ease piston out of bore. 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.
3. Use screwdriver to pry boot out of caliper housing. Pry piston seal from its groove in caliper bore with a piece of wood or plastic. Do not use metal tool of any type to remove piston seal. Remove bleeder valve from housing.

Inspection

1. Boot, seal, rubber bushings, and sleeves are to be replaced each time caliper is overhauled. Clean all other parts in denatured alcohol. Dry parts with dry compressed air. NOTE: Using lubricated shop air will leave a film of mineral oil on metal parts. This may damage rubber parts upon contact during reassembly.
2. Check guide pins for corrosion, breaks in plating or other damage. Do not attempt to clean pins; replace them. Check outside diameter of piston for scoring, nicks, corrosion, and worn or damaged plating. If surface defects exist, piston must be replaced.
3. Piston bore should be checked for similar defects. Bore is not plated, therefore, it may be polished with crocus cloth. Thoroughly clean after polishing. Replace caliper housing if bore corrosion cannot easily be cleaned out.

Using Compressed Air to Remove Caliper Piston Compressed air must be filtered and dry. Scheme 12

1. Lubricate bore in caliper housing and new piston seal with clean brake fluid. Position seal in caliper bore groove.
2. Lubricate piston with clean brake fluid and assemble new boot into groove in piston with fold facing open end of piston.
3. Insert piston into caliper bore using care not to unseat seal. Force piston to bottom of bore. Position outer diameter of boot in caliper counterbore and drive in until fully seated.
4. Check boot installations to ensure retaining ring (molded into boot) is not bent, and that boot is installed completely below caliper face. Install brake hose, using new copper gasket.

1. Raise vehicle and support with safety stands. Remove wheel assembly and brake drum. It may be necessary to back off brake shoe adjustment before removing drum. Unlock primary and secondary shoe springs. Remove shoe hold down springs.
2. Lift up on actuator, unhook actuating link from anchor pin and remove link. Spread shoes enough to clear wheel cylinder links. Remove parking brake strut and spring. Disconnect cable from lever. Remove brake shoes.

1. Lubricate fulcrum end of parking brake lever with brake lubricant. Attach lever to secondary shoe. Make sure lever moves free. Connect brake shoes together with adjuster spring.
2. Place adjuster screw in position. Make sure spring does not contact starwheel portion of adjusting screw. Right hand thread adjusting screw should be on left side.
3. Make sure starwheel lines up with hole in backing plate. Apply a thin coating of brake lubricant to contact surface on backing plate. Position brake shoes on backing plate.
4. Primary shoe (short lining) is to front. Connect cable to parking brake lever. Install strut between shoes. Install actuator, return spring and actuator link. Install shoe hold down springs.
5. Install both primary and secondary shoe springs. Measure inside diameter of brake drum with measuring gauge (J-21177). Expand brake shoes to dimension obtained on outside caliper portion of tool.
6. Install brake drum and wheel assembly. Bleed system if any portion of hydraulic system was opened. Check fluid level in master cylinder and add as necessary.

1. Remove reservoir cover and diaphragm. Discard remaining brake fluid in reservoir. Push in on primary piston and remove snap ring.
2. Apply compressed air at forward brake line hole while plugging rear hole. Pistons will be forced out at open end of master cylinder.
3. Remove spring retainer and seals from secondary piston. Discard seals. Clamp mounting ear of master cylinder in vise and pry off reservoir.
4. Do not attempt to remove take-up valve from master cylinder. It is not a serviceable component. Remove reservoir grommets and discard.

Quick Take-Up Master Cylinder ("S" Series Shown). Scheme 13

Inspect cylinder bore for scoring or corrosion. If signs of corrosion are evident, master cylinder must be replaced. No abrasives, of any kind, are to be used on cylinder bore.

1. Lubricate new reservoir grommets with silicone brake lube and press into master cylinder. Make sure grommets are properly seated. Lay reservoir on flat, hard surface. On Astro and Safari models, place block of wood under front reservoir to bring up to level of rear reservoir.
2. Rock master cylinder body onto reservoir until completely seated. Lubricate new piston seals and install on secondary piston, with lip of seals towards ends of piston. Install spring retainer.
3. Install secondary piston spring and secondary piston assembly in master cylinder. Lubricate primary piston seals with clean brake fluid.
4. Install primary piston in master cylinder. Press in piston and install snap ring. Fit diaphragm in reservoir cover and install cover.

Remove rubber boots from ends of cylinder. Remove piston return spring, cylinder cups, and pistons from cylinder. Remove bleeder screw and inspect bore for damage.

If bore of cylinder is pitted and/or scratched, hone or replace as needed. Soak rubber cylinder cups in brake fluid or assembly lube and reverse disassembly procedures.

Lateral Runout

Adjust wheel bearings until all end play is eliminated. Attach dial indicator with contact tip of indicator about 1" from rotor edge. Set indicator to zero and turn rotor through one complete revolution, noting indicator reading.

Parallelism

Check thickness of rotor at 4 or more points around circumference of rotor. Make all measurements at same distance from edge of rotor. If thickness variation is excessive, refinish or replace rotor as necessary.

TORQUE SPECIFICATIONS

TIGHTENING SPECIFICATIONS

DISC BRAKE SPECIFICATIONS

DISC BRAKE ROTOR SPECIFICATIONS

DRUM BRAKE SPECIFICATIONS

DRUM BRAKE SPECIFICATIONS