Disc & Drum Hyundai Excel I

BRAKE SYSTEM

Brake system is hydraulically-operated using a master cylinder with a single reservoir and 2 outlets. A vacuum power brake unit is used on all models. A proportioning valve is used to control braking action. Brake system is self-adjusting.

ADJUSTMENTS

Note. If parking brake lever stroke is not to specification and cables at equal length after adjustment, automatic adjuster will malfunction.

PARKING BRAKE

1. Properly adjusted parking brake lever stroke should be 5-7 notches (clicks) at 44 lbs. (20 kg). If not, remove console box and release brake lever. Adjust cable adjusting nuts, allowing enough slack in cables to prevent brake shoe drag. (Scheme 1)
2. Loosen parking brake switch mounting bolt. Adjust switch until indicator light goes out when brake lever is fully released and light comes on when lever is pulled one notch. Ensure rear brakes do not drag with brake lever released.

Parking Brake Cable Adjustment. Scheme 1

PROPORTIONING VALVE FUNCTION TEST

1. Attach 2 pressure gauges that measures at least 2000 psi (140.6 kg/cm 2 ), to the input and output side of proportioning valve. (Scheme 2) Measure the input and output pressure with brakes applied. Compare pressure readings with PROPORTIONING VALVE PRESSURE CHART. (Scheme 3)
2. If measured pressures are NOT within range, replace proportional valve. Measure both left and right pressure readings. If the difference in pressure is 60 psi (27 kg/cm 2 ), replace proportioning valve. DO NOT disassemble proportioning valve.

Testing Proportioning Valve. Scheme 2

Proportioning Valve Pressure Chart. Scheme 3

Functional Test

1. Run engine for 2 minutes. Turn off engine. Step on brake pedal several times with normal pressure. If brake pedal depresses fully the first time but gradually becomes higher when depressed succeeding times, power brake unit is operating properly. If pedal height remains the same, power brake unit is defective.
2. With engine not running, step on brake pedal several times. Ensure that brake pedal height remains the same. Depress brake pedal and start engine. If pedal moves downward slightly, power brake unit is okay. If there is no change, power brake unit is defective.
3. With engine running, step on brake pedal and turn off engine. Hold pedal in depressed position for 30 seconds. If pedal height does not change, power brake unit is okay. If pedal rises, power brake unit is defective. If all 3 tests are okay, power brake unit is functioning. If one test fails, test vacuum hose, check valve or power brake unit for defects.

Removal

1. Raise and support vehicle. Remove front wheel. Remove pad protector by prying up edge of clip at center of protector. (Scheme 4) Hold center of "M" clip with a screwdriver. Detach "M" clip from pad and its ends from retaining pins.
2. Remove "M" clip. Using pliers, remove "K" spring. Remove pad retaining pins. Remove pads and anti-squeak shim by gripping backing plate area of pad and shim with pliers. CAUTION: Ensure that torque plate shaft is clean. Caliper and bushing will experience premature wear if shaft is coated with dust or mud.

Installation

Replace pads in set of 4. Press piston to bottom of bore. Install "K" spring, "M" clip, pad assembly and anti-squeak shim on support mounting. (Scheme 5) Lower caliper body and install retaining pin. Pad thickness wear limit is.040" (1.0 mm).

Installing Pad Protector. Scheme 4

Installing Spring & Clip on Brake Pads. Scheme 5

Removal & Installation

Remove disc pads. Pull out hose clip from strut area. Disconnect brake hose from caliper. Remove caliper. To install, reverse removal procedure. Tighten bolts to specification and bleed brake system.

1. Remove wheels. Remove undercover. Remove lower arm ball joint and strut bar from lower arm. Measure disc runout. Disc runout is.006" (.15 mm) or less. Rotor thickness is.510-.450" (13.0-11.4 mm). Remove center cap. Loosen drive shaft nut.
2. Remove caliper assembly. Remove drive shaft. See «AXLE SHAFTS - FRONT»(/hyundai/excel/i-1985-1989/remont/axle-shafts/#axle-shafts-front). Disconnect tie rod from knuckle. Remove knuckle, hub and rotor as an assembly.
3. Mount steering knuckle in a soft-jawed vise. Drive out hub and rotor assembly with a soft hammer. Remove preload adjusting spacer from hub. Remove bolts attaching rotor to hub. (Scheme 6) Remove rotor from hub assembly.

Install rotor on hub. (Scheme 6) Tighten bolts to specification. Press hub into knuckle. Install new inner oil seal. Slide drive shaft into position. Install knuckle assembly by reversing removal procedures. See TIGHTENING SPECIFICATIONS.

Scheme 6

Raise and support vehicle. Remove brake drum. Remove clip springs. Disconnect shoe retainer spring, shoe-to-shoe spring and shoe hold-down spring. Remove shoes and adjuster as an assembly. Replace brake shoes if lining thickness is .04" (1.0 mm) or less.

Installatin

To install, reverse removal procedure. Apply Lubriplate to all shoe contact points, adjuster assembly and parking brake attachment. Set adjustment lever all the way back. Adjust brake shoes to specification. Install brake drum. Depress brake pedal to adjust shoe clearance. Adjust parking brake and warning light to specifications, if necessary. (Scheme 7)

Exploded View of Leading/Trailing Shoe Rear Brake Assembly. Scheme 7

Remove fluid level sensor harness connector. Disconnect brake lines from master cylinder. Slowly depress brake pedal several times to drain fluid from cylinder housing. Remove master cylinder from brake booster unit. Separate reservoir from housing.

To install master cylinder, reverse removal procedure. Adjust clearance between brake booster push rod and master cylinder piston. Clearance is .016-.031" (.40-.80 mm). After installation, adjust pedal height. Bleed brake system.

POWER BRAKE UNIT CHECK VALVE REPLACEMENT

Note. Test check valve before removal. Disconnect vacuum hose on booster side of check valve. Place finger over check valve. Start engine. Vacuum should be felt.

Remove hose clamps from both ends of check valve. Remove check valve clamp. Remove check valve. To install, coat both ends of check valve with sealer. Install check valve with arrow pointing toward intake manifold side. Install check valve clamp and vacuum hoses. Secure hose clamps. (Scheme 8)

Power Brake Check Valve. Scheme 8

Remove brake master cylinder. Disconnect vacuum hose from power brake unit. Disconnect brake pedal and operating rod of power brake unit. From inside vehicle, remove 4 nuts attaching power brake unit to firewall. Remove power brake unit. To install, reverse removal procedure. Bleed brake system.

Disassembly

Remove dust boot. Apply compressed air to fluid inlet to remove piston. Remove piston seal without damaging caliper bore or seal groove. (Scheme 9)

Cleaning & Inspection

Clean dust boot and other rubber parts in alcohol only. Clean all other parts with alcohol or brake fluid. Inspect caliper bore and piston for wear, damage or rust. Replace piston seal and dust boot. Replace any other worn or defective part.

Note. Repair kits contain proper lubricants to be used during reassembly.

Reassembly

Coat piston seal with rubber grease. Slide seal into groove in cylinder bore. Slip piston into bore. Ensure that seal is not twisted. Lightly coat dust seal groove with recommended rubber grease. Fit dust boot into place. Refit cylinder to caliper.

Note. Possible cause of increased pedal stroke is insufficient fit between piston and piston seal. Correct by manually levering piston to seat several times. This will create a better fit between piston and seal. Ensure brake pad is removed during this procedure.

Exploded View of Front Disc Brake Caliper. Scheme 9

Place cylinder in a soft-jawed vise. Remove reservoir. Remove piston stop bolt, while depressing piston. Remove piston stopper ring. Withdraw primary piston assembly and secondary piston assembly from master cylinder body. (Scheme 11)

Note. Do not disassemble primary and secondary piston assembly.

Inspect master cylinder bore and piston for wear or other damage. Check clearance between cylinder bore and piston. Clearance should not exceed .006" (.15 mm). If any parts are found worn or defective, replace part assembly.

Reverse disassembly procedure. Before reassembly, apply rubber grease to all parts (except boots). Ensure that return port is not blocked by piston cup when piston is at return position.

Exploded View of Power Brake Unit. Scheme 10

Disassembled View of Master Cylinder. Scheme 11

Clean exterior of power brake unit. Install Holder (09591-21000) on power brake unit. Place unit in vise, with jaws on holder. Fabricate 2 steel pipes and attach them to Plate (09591-21100). (Scheme 11) Attach pipes and plate to rear shell. Turn rear shell counterclockwise. Remove rear shell. Disassemble power brake unit. (Scheme 10)

Inspection

Check all parts for wear and damage. Replace any worn or damaged part.

To reassemble, reverse disassembly procedure. Apply silicone grease to rod seal lip, push rod and rod body perimeter, reaction disc, valve body seal lip bearing, diaphragm plate and diaphragm-to-shell mating surfaces.

Fabricated Steel Pipe Dimensions. Scheme 12

TIGHTENING SPECIFICATIONS

TIGHTENING SPECIFICATIONS

DISC BRAKE ROTOR SPECIFICATIONS

DISC BRAKE ROTOR SPECIFICATIONS

DRUM BRAKE SPECIFICATIONS

DRUM BRAKE SPECIFICATIONS

See also:
• AXLE SHAFTS - FRONT
• TIGHTENING SPECIFICATIONS