Disc & Drum Brake System Buick Century V

DESCRIPTION & OPERATION

Front brakes are disc and rear brakes are drum. ABS brakes are standard. Components common to ABS and Non-ABS systems are covered in this article. For specific ABS components, see ANTI-LOCK BRAKE SYSTEM - ABS-VI article.

Hydraulic system is diagonally split so system will still operate if one side loses pressure. Proportioning valves on master cylinder limit hydraulic pressure applied to rear brakes, directing most of the available hydraulic pressure to the front brakes.

Front disc brakes may be a single or dual piston assembly. Disc brakes are continually self-adjusting. Caliper piston seals retract pistons enough to allow brake lining to lightly brush rotor. Sliding caliper compensates for lining wear.

A BRAKE warning light is located in the instrument cluster. BRAKE warning light will come on if parking brake is not fully released, a system failure, or brake fluid level in master cylinder reservoir is low. A bulb check is provided when ignition switch is in START position. Warning light should go off when ignition switch returns to RUN position.

BRAKE WARNING INDICATOR INOPERATIVE

See appropriate INSTRUMENT PANEL article listed below.

1. «INSTRUMENT PANEL - ANALOG»(/buick/century/v-1982-1996/remont/gauges-instrument-panels/#instrument-panel-analog) - Century
2. «INSTRUMENT PANEL - ANALOG»(ref-30630) - Cutlass Ciera
3. «INSTRUMENT PANEL - ANALOG»(ref-30631) - Cutlass Cruiser

BLEEDING BRAKE SYSTEM

MANUAL BLEEDING

See Manual Bleeding in ANTI-LOCK BRAKE SYSTEM - ABS-VI article.

PRESSURE BLEEDING

See Pressure Bleeding in ANTI-LOCK BRAKE SYSTEM - ABS-VI article.

BRAKE PEDAL HEIGHT & FREE PLAY

Brake pedal height and free play is not adjustable. See BRAKE PEDAL TRAVEL .

BRAKE PEDAL TRAVEL

Note. Brake pedal travel is not adjustable. Use the following procedure to determine if brake pedal travel is as specified.

1. Most low brake pedal or excessive pedal travel problems are caused by air in hydraulic system. Bleed hydraulic system before continuing procedure. See Manual Bleeding section in «ANTI-LOCK BRAKE SYSTEM - ABS-VI»(/buick/century/v-1982-1996/remont/anti-locktraction-control/#anti-lock-brake-system-abs-vi) article. Other possible causes of excessive pedal travel are incorrect power booster pushrod length, parking brake adjustment, frozen rear brake shoe adjustors, worn linings, or a leak in hydraulic system.
2. With engine off, pump brake pedal until all vacuum reserve is exhausted from power brake booster. A definite change in pedal feel will occur. Install Brake Pedal Effort Gauge (J-28662) onto brake pedal. Hook end of tape measure over top of brake pedal. Measure and record distance to rim of steering wheel.
3. Apply 100 lbs. (45 kg) of force to brake pedal. Measure and record distance to rim of steering wheel again. Difference between measured values is brake pedal travel. If brake pedal travel exceeds specification, adjust rear brake shoes. See BRAKE PEDAL TRAVEL SPECIFICATIONS table. See REAR BRAKE SHOES under «ADJUSTMENT»(/buick/century/v-1982-1996/remont/mechanical-hydraulic/#disc-drum-brake-system) .

BRAKE PEDAL TRAVEL SPECIFICATIONS

REAR BRAKE SHOES

Note. Adjustment is only required if shoes have been serviced or length of adjusting screw has been changed.

1. Release parking brake. Raise and support vehicle. Mark relationship of wheels to wheel studs. Remove wheels. Mark relationship of drums to wheel studs. Remove drum. If drum is easily removed, go to step 4). If drum is difficult to remove, go to next step.
2. Release parking brake and back off parking brake adjuster. Remove access hole plug on backing plate. Insert screwdriver through hole and back off brake adjustment. This allows shoes to retract slightly.
3. Apply a small amount of penetrating oil around pilot hole at center of drum to break corrosion seal between drum and wheel stud flange. Remove drum. Insert rubber plug into access hole to prevent contamination.
4. Ensure lever stop on parking brake lever is against edge of brake shoe web. If parking brake cable is holding lever stop off edge of shoe web, loosen parking brake cable adjuster. (Scheme 4) Measure inner diameter of brake drums. At each brake assembly, turn star wheel on adjusting screw assembly until brake shoe diameter is.050" (1.27 mm) less than inner diameter of drum.
5. Install drums and wheels, aligning marks made during removal. Tighten wheel lug nuts to specification. See «TORQUE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical-hydraulic/#disc-drum-brake-system) table. Lower vehicle. Firmly apply and release service brakes 30-35 times using normal braking force, pausing about one second between brake applications. Adjust parking brake (if necessary). See PARKING BRAKE (DRUM) under «ADJUSTMENTS»(/buick/century/v-1982-1996/remont/mechanical-hydraulic/#disc-drum-brake-system).

PARKING BRAKE (DRUM)

Note. If brakes have been serviced, adjust parking brake to prevent premature brake wear. Clean and lubricate threaded rod on parking brake adjuster before turning adjuster.

1. Adjust rear brake shoes. See REAR BRAKE SHOES under «ADJUSTMENTS»(/buick/century/v-1982-1996/remont/mechanical-hydraulic/#disc-drum-brake-system). Apply parking brake to 10 clicks (ratchets) and release. Do this 5 times.
2. To ensure parking brake pedal is fully released, turn ignition on. BRAKE indicator light will come on during BULB TEST and go out. If light goes off, go to next step. If light does not go off, operate manual release lever on parking brake assembly and pull front parking brake cable downward. This should fully release pedal.
3. Raise and support vehicle. At parking brake cable adjuster, rotate adjuster nut until a 1/8" (3.2 mm) drill bit can be inserted through access hole into space between shoe web and parking brake lever. (Scheme 4) Cable is adjusted when a 1/8" (3.2 mm) drill bit will fit into space but a 1/4" (6.4 mm) drill bit will not fit.
4. Apply parking brake to 4 clicks. Wheels should not turn when trying to turn wheels forward by hand. Wheels should drag or not turn when trying to turn wheels in reverse direction by hand. Release parking brake. Ensure wheels rotate freely. Install access hole plugs. Lower vehicle.

POWER BRAKE BOOSTER PISTON ROD

Note. Use the following procedure to measure how far booster piston rod protrudes from booster when vacuum is applied to booster. Piston rod is not adjustable. If piston rod protrusion is out of limits, replace power brake booster assembly.

Booster does not have to be installed to perform procedure. Apply 25 in. Hg vacuum or MAXIMUM available engine vacuum to booster. Position Piston Rod Gauge (J-37839) over piston rod. (Scheme 1) One side of gauge measures minimum rod length. Other side measures maximum rod length. If piston rod length does not fall between maximum and minimum dimensions, replace brake booster assembly.

Scheme 1

BRAKELIGHT SWITCH

Hold brake pedal in applied position. Press switch fully forward until switch body is seated. Pull brake pedal fully rearward against pedal stop. Switch is now adjusted. Ensure no clicks are heard when pedal is pulled up and brakelights do not stay on with brake pedal at rest (unapplied). Switch should open at .125-.500" (3.2-12.7 mm) of brake pedal travel measured at centerline of brake pedal pad. Brakelight switch should open .188" (4.76 mm) of brake pedal travel after cruise control switch opens.

Removal

1. Remove and discard 2/3 of brake fluid from master cylinder reservoir to prevent overflow when servicing. Raise and support vehicle. Mark wheel in relation to hub. Remove front wheel. Install and finger-tighten 2 lug nuts with flat side toward rotor to hold rotor when caliper is removed.
2. Position "C" clamp with stationary end of clamp on caliper housing and threaded end on outboard pad. Tighten "C" clamp until piston(s) are pushed into bore far enough to slide caliper off of rotor. Remove "C" clamp.
3. If not completely removing caliper, go to next step. If completely removing caliper (such as for overhaul), remove bolt securing brake hose to caliper. Disconnect brake hose from caliper. Plug opening in brake hose and caliper to prevent fluid loss and contamination.
4. Remove caliper bolts and bushings. (Scheme 2) Remove caliper. If brake hose is still connected to caliper, wire aside so brake hose will not be damaged. Remove pads from caliper.

Installation

1. Liberally coat inner diameter of bushings with silicone grease. Install caliper. Install caliper bolts and bushings. If bolts slide through bushings using hand pressure, go to step 3).
2. If bolts do not slide through bushings using hand pressure, remove bolts and bushings. Inspect caliper bores for corrosion. Clean bores with clean denatured alcohol. Install and lubricate bushings. Install caliper bolts.
3. Tighten caliper bolts to specification. See «TORQUE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical-hydraulic/#disc-drum-brake-system) table. If brake hose was not disconnected, go to next step. If brake hose was disconnected, connect brake hose to caliper. Tighten fitting bolt to specification. Bleed brake hydraulic system, and go to next step. See «BLEEDING BRAKE SYSTEM»(/buick/century/v-1982-1996/remont/mechanical-hydraulic/#disc-drum-brake-system__bleeding-brake-system) .
4. Apply brakes several times to seat pads. Install wheel, aligning marks made during removal. Tighten wheel lug nuts to specification. Fill brake fluid reservoir. Road-test vehicle.

Remove caliper. See FRONT BRAKE CALIPER. Remove outer pad from caliper, using screwdriver to disengage pad retaining buttons. (Scheme 2) Remove inner pad.

1. Clean outside surface of caliper piston(s) boot with denatured alcohol. (Scheme 2) Slowly compress piston(s) into bore with a "C" clamp, being careful not to cock piston(s) to one side or damage piston boot. See «FRONT BRAKE CALIPER»(/buick/century/v-1982-1996/remont/mechanical-hydraulic/#disc-drum-brake-system). Using small plastic or wood tool, lift inner edge of boot next to piston and press out any trapped air. Reposition boot so it lays flat with convolutions in proper position.
2. Install inner pad, snapping retainer into place in piston(s). Ensure pad lays flat against piston(s). Ensure boot(s) is not touching pad. Install outer pad with wear sensor facing downward. Ensure pad lays flat against caliper.
3. To install remaining components, reverse removal procedure. Tighten bolts to specification. See «TORQUE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical-hydraulic/#disc-drum-brake-system) table.

Removal & Installation

Remove caliper and wire aside. See FRONT BRAKE CALIPER . Mark rotor in relation to hub for installation reference. Remove rotor. To install, reverse removal procedure. Tighten nuts and bolts to specification. See TORQUE SPECIFICATIONS table.

Note. Manufacturer does not recommend resurfacing rotors when replacing brake pads. Resurfacing rotors is allowed when there is a brake pulsation complaint or scoring greater than .060" (1.5 mm). See FRONT OR REAR ROTOR RESURFACING SPECIFICATION table.

FRONT OR REAR ROTOR RESURFACING SPECIFICATIONS (1)

Note. Observe position of springs, adjuster assembly and brake shoes for reassembly reference.

1. Release parking brake. Raise and support vehicle. Mark wheels in relation to wheel studs. Remove wheels. Mark drums in relation to wheel studs. Remove drums. If drums are easily removed, go to step 4). If drums are difficult to remove, go to next step.
2. Back off parking brake cable adjustment. Remove access hole plug from backing plate. (Scheme 4) Insert screwdriver through hole and back off adjusting screw. Insert rubber plug into access hole to prevent contamination.
3. Apply a small amount of penetrating oil around pilot hole at center of drum to break corrosion seal between drum and wheel stud flange. Remove drums. WARNING: When removing and installing actuator spring, keep fingers away from spring to prevent them from being pinched between spring and shoe web or between spring and backing plate. DO NOT stretch actuator spring more than necessary or spring tension will be reduced.
4. Disconnect actuator spring from adjuster actuator and web of parking brake shoe. Disconnect retractor spring from adjuster shoe so end of spring snaps off of shoe web onto backing plate.
5. Remove adjuster shoe, adjuster actuator and adjusting screw assembly. Disconnect parking brake lever from parking brake shoe. DO NOT disconnect parking brake cable from parking brake lever unless replacing lever.
6. Disconnect retractor spring from parking brake shoe so end of spring snaps off of shoe web onto backing plate. Remove parking brake shoe. Remove retractor spring.

1. Using brake lubricant, lubricate 6 raised shoe pads on backing plate and anchor surfaces where bottom of shoes make contact. (Scheme 4) Install retractor spring, hooking center section of spring under tab on anchor. Position parking brake shoe onto backing plate.
2. Pull end of retractor spring up to rest on web of parking brake shoe. Pull end of retractor spring over until it snaps into slot of parking brake shoe web. Connect parking brake lever to parking brake shoe. Connect parking brake cable to parking brake lever (if disconnected).
3. Disassemble, clean and lubricate adjuster screw assembly. Install adjuster screw assembly and adjuster shoe (without adjuster actuator), ensuring components correctly engage slotted ends of adjuster screw assembly. Engage end of retractor spring into slot of adjuster shoe web.
4. Lubricate tab and pivot point on adjuster actuator with brake lubricant. Spread brake shoes and work adjuster actuator into position. Install actuator spring, first engaging "U"-shaped end of spring into hole in parking brake shoe web.
5. Ensure lever stop on parking brake lever is against edge of brake shoe web. If parking brake cable is holding lever stop off edge of shoe web, loosen parking brake cable adjuster. Measure inner diameter of brake drums. At each brake assembly, turn star wheel on adjusting screw assembly until brake shoe diameter is.050" (1.27 mm) less than inner diameter of drum.
6. Install drums and wheels, aligning marks made during removal. Tighten wheel lug nuts to specification. See «TORQUE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical-hydraulic/#disc-drum-brake-system) table. Lower vehicle. Firmly apply and release service brakes 30-35 times using normal braking force, pausing about one second between brake applications. Adjust parking brake. See PARKING BRAKE (DRUM) under «ADJUSTMENTS»(/buick/century/v-1982-1996/remont/mechanical-hydraulic/#disc-drum-brake-system).

Remove rear brake shoes. See REAR BRAKE SHOES. Disconnect inlet tube nut and line. Plug opening in line to prevent fluid loss and contamination. Remove wheel cylinder bolts and wheel cylinder. (Scheme 4) To install, reverse removal procedure. Tighten nuts and bolts to specification. See TORQUE SPECIFICATIONS table. Bleed brake system. See BLEEDING BRAKE SYSTEM.

MASTER CYLINDER

Removal (With ABS)

1. Using Tech 1 scan tester, perform gear tension release procedure. See Tech 1 scan tester instructions for more information.
2. Disconnect fluid level sensor electrical connector. Disconnect electrical connectors from both solenoids. Disconnect motor pack 3-pin and 6-pin connectors. Disconnect brakelines from ABS hydraulic modulator. Plug lines and openings in ABS hydraulic modulator. DO NOT allow any brake fluid to enter motor pack or electrical connectors. Remove nuts securing master cylinder to booster. Remove ABS hydraulic modulator/master cylinder assembly.
3. Remove 2 Torx head screws securing gear cover to bottom of ABS hydraulic modulator. Remove gear cover. Remove 4 Torx head screws securing motor pack to ABS hydraulic modulator. Remove motor pack. Remove 2 banjo bolts securing ABS hydraulic modulator to master cylinder. Separate ABS hydraulic modulator from master cylinder. Remove 2 transfer tubes installed between ABS hydraulic modulator and master cylinder. Remove banjo bolt "O" rings from ABS hydraulic modulator and master cylinder.

1. Lubricate NEW "O" rings with clean brake fluid. Set "O" rings into position. Install transfer tubes into ports on ABS hydraulic modulator, pressing tubes by hand until bottomed in bore. Clamp mounting flange of master cylinder in vise.
2. Holding ABS hydraulic modulator, rock it into position on master cylinder, inserting transfer tubes into master cylinder ports. Install bolts securing ABS hydraulic modulator to master cylinder. Tighten bolts to specification. See «TORQUE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical-hydraulic/#disc-drum-brake-system) table.
3. With ABS hydraulic modulator upside down (gears facing up), rotate each gear counterclockwise until stopped. This positions pistons close to top of modulator bore, simplifying brake bleeding procedure. To install remaining components, reverse removal procedure. Bleed brake system. See «ANTI-LOCK BRAKE SYSTEM - ABS-VI»(/buick/century/v-1982-1996/remont/anti-locktraction-control/#anti-lock-brake-system-abs-vi) article.

POWER BRAKE BOOSTER

Note. Power brake booster can be removed without completely removing master cylinder, but if both components are to be removed, remove master cylinder first.

Remove nuts securing master cylinder to booster. Without disconnecting hydraulic lines, remove master cylinder from booster and position aside. Disconnect vacuum hose from booster check valve. Under instrument panel, remove nuts securing booster to firewall. Without putting undue sideways pressure on push rod, tilt booster slightly to work push rod off of brake pedal. Remove booster.

To install, reverse removal procedure. Tighten nuts to specification. See TORQUE SPECIFICATIONS table. Adjust brakelight switch. See BRAKELIGHT SWITCH under ADJUSTMENTS .

Remove fluid reservoir from master cylinder (if necessary). Remove proportioning valve caps, "O" rings and springs. (Scheme 3) Remove pistons with needle nose pliers, being careful not to damage piston stems. Separate seals from pistons.

Clean part in denatured alcohol. Replace pistons if corroded or deformed. Lubricate NEW "O" rings, NEW piston seals and piston stems with silicone grease supplied in repair kit. (Scheme 3) Install seals onto pistons with seal lips facing upward. To install remaining components, reverse removal procedure.

REAR AXLE HUB & BEARING ASSEMBLY

1. Raise and support vehicle. Remove wheel and brake drum. Bolts securing hub and bearing assembly also secure brake backing plate. Suspend brake backing plate with wire so it will not be suspended by brakeline or ABS wiring when bolts are removed.
2. Remove bolts securing hub and bearing assembly. Remove hub and bearing assembly. To install, reverse removal procedure. Tighten nuts and bolts to specification. See «TORQUE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical-hydraulic/#disc-drum-brake-system) table.

OVERHAUL

Note. For overhaul procedures, use exploded views. (Scheme 2)- (Scheme 4).

Scheme 2

Scheme 3

Scheme 4

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

DISC BRAKE SPECIFICATIONS

DISC BRAKE SPECIFICATIONS

DRUM BRAKE SPECIFICATIONS

DRUM BRAKE SPECIFICATIONS

See also:
• ANTI-LOCK BRAKE SYSTEM - ABS-VI
• INSTRUMENT PANEL - ANALOG
• BRAKE PEDAL TRAVEL
• ADJUSTMENT
• BLEEDING BRAKE SYSTEM