�

1993 Jeep Cherokee

1993 BRAKES

Chrysler Corp. - Disc & Drum

Jeep; Cherokee, Grand Cherokee, Grand Wagoneer, Wrangler

DESCRIPTION

Floating caliper disc brake assembly uses a single piston caliper which floats on 2 bolts. As brake pedal is depressed, hydraulic pressure passes through a proportioning valve to brake caliper piston.

This force is transmitted to inboard brake pad, forcing it against braking surface of rotor. Pressure then moves outer caliper housing and pad inward on caliper mounting bolts, forcing outer pad against outer braking surface of rotor.

A combination proportioning valve/pressure differential switch is used on all models. Proportioning valve is not serviceable. Valve must be replaced if it malfunctions.

A pressure differential brake warning light switch is used to warn vehicle operator that one side of the hydraulic system 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 one side of brake system fails, hydraulic pressure moves piston toward failed side. Shoulder of piston contacts switch terminal, grounding brake warning light.

Proportioning valve operates by restricting hydraulic pressure to rear brakes at a given ratio when system hydraulic pressure reaches a certain point. This improves front-to-rear brake balance during 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.

BLEEDING BRAKE SYSTEM

NOTE: Brake bleeding procedures for models with anti-lock brakes are not covered in this article. See ANTI-LOCK BRAKE SYSTEM article for proper procedure.

BLEEDING SEQUENCE

Before bleeding system, exhaust all vacuum from power unit by depressing brake pedal several times. When bleeding disc brakes, air may tend to cling to caliper walls. To aid in removal of air, lightly tap caliper while bleeding.

Fill master cylinder with clean brake fluid. Fluid should meet DOT 3 specifications. Bleed master cylinder with bleeder valves (if equipped). Bleed wheel cylinders and calipers in sequence. See BRAKELINE BLEEDING SEQUENCE table.

BRAKELINE BLEEDING SEQUENCE TABLE

Application Sequence

All Models RR, LR, RF, LF

MASTER CYLINDER BLEEDING

Bench Bleeding

1. Master cylinder must be bled before installation to
   prevent excessive amounts of air from entering hydraulic system,
   creating poor brake operation.

2. Place master cylinder in soft-jawed vise. DO NOT tighten
   vise enough to damage master cylinder. Install bleed tubes in both
   outlets of master cylinder. See Fig. 1.

3. Fill master cylinder with clean brake fluid. Fluid should
   meet DOT 3 specifications. Ensure end of bleed tubes are submerged in
   brake fluid.

4. Using proper size rod, apply and release master cylinder
   until no air bubbles exist in brake fluid flow. When all air bubbles
   are gone from master cylinder, cap outlet ports. Install reservoir
   cover and seal. Install master cylinder and bleed on vehicle.

Fig. 1: Bleeding Master Cylinder (Typical) Courtesy of Chrysler Motors.

On-Vehicle Bleeding

5. Install master cylinder on vehicle after bench bleeding.
   Remove bleeder lines and install brakelines. DO NOT tighten brakelines
   yet.

6. Slowly force brake pedal to floor and hold in this
   position. Tighten brakelines, and release brake pedal. Repeat
   procedure until no air bubbles exist at brakelines. Tighten

brakelines. Check for leaks. PRESSURE BLEEDING

CAUTION: Front brake metering valve is located in front end of

combination valve. Valve stem MUST be pressed inward or held outward slightly to bleed front brakes.

7. Clean master cylinder cap and surrounding area. Remove
   cap. With pressure tank at least 1/2 full, connect to master cylinder
   with adapters. Attach bleed hose to first bleeder valve to be
   serviced. See BRAKELINE BLEEDING SEQUENCE table under BLEEDING
   SEQUENCE.

8. Place other end of hose in clean glass jar partially
   filled with clean brake fluid so end of hose is submerged in fluid.

9. Open release valve on pressure bleeder. Follow equipment
   manufacturer�s pressure instructions or see PRESSURE BLEEDER SETTINGS
   table. Open bleeder valve 3/4 turn, and note fluid flow.

10. Close bleeder screw when fluid is free of bubbles. Repeat
    procedure on remaining wheels in proper sequence. Check brake pedal
    operation after bleeding has been completed.

11. Remove pressure bleeding equipment and valve retainer from
    hold-off valve. Ensure master cylinder is full of fluid. Check for
    leaks.

PRESSURE BLEEDER SETTINGS TABLE

Application psi (kg/cm²)

All Models 15-20 (1.1-1.4)

MANUAL BLEEDING

NOTE: Some models are equipped with anti-lock brake system. See ANTI-LOCK BRAKE SYSTEM article for bleeding procedure.

Cherokee & Wrangler

12. Fill master cylinder with clean brake fluid. Fluid should
    meet DOT 3 specifications. Open ALL bleed valves. Close bleeder valves
    when fluid begins flowing from each valve. Refill master cylinder.

13. Install bleed hose to first bleeder valve to be serviced.
    See BRAKELINE BLEEDING SEQUENCE table under BLEEDING SEQUENCE.
    Submerge other end of hose in clean glass jar partially filled with
    clean brake fluid. See Fig. 2.

NOTE: Ensure bleeder valve is closed when brake pedal is released. DO NOT allow master cylinder to run out of fluid.

3) Open bleeder valve 3/4 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.

ADJUSTMENTS

BRAKE PEDAL

Brake pedal push rod length is preset by manufacturer. No adjustment is possible.

PARKING/EMERGENCY BRAKE

Cherokee & Wrangler

14. Adjust rear brakes. See REAR BRAKE SHOES under ADJUSTMENTS
    . Check cable for binding, kinking or fraying. Replace cable as
    required. Apply and release parking brake 5 times.

15. Place parking brake lever in fifth notch. Raise and
    support vehicle. Position Adjustment Gauge (J-34651) on one of rear
    parking brake cables. See Fig. 3. Apply and hold a torque of 50 INCH
    lbs. (6 N.m) on adjustment gauge, and note position of gauge pointer.

16. If adjustment gauge pointer is not within okay band, turn
    parking brake cable equalizer adjustment nut in or out until pointer
    is within okay band. Remove tools, and lower vehicle. Ensure proper
    parking brake operation.

30086

Fig. 3: Adjusting Parking Brake Courtesy of Chrysler Motors.

(Cherokee & Wrangler)

. Check cable for binding, kinking or fraying. Replace cable as required.

17. Fully apply parking brake. Raise and support vehicle. Mark
    position of adjusting nut on threaded end of cable tensioner. Tighten
    adjusting nut about 1/2" (13 mm). Replace tensioner if there are not
    enough threads for proper adjustment.

18. Lower vehicle until wheels are about 6" off floor. Release
    parking brake. Verify that rear wheels rotate freely and no drag is
    felt. Lower vehicle, and ensure parking brake operates properly.

REAR BRAKE SHOES

NOTE: Brakes are self-adjusting. Under normal circumstances,

manual adjustment is only required if shoes are removed. Replace brake shoes when lining is 1/16" on bonded linings and 1/32" from rivet on riveted linings.

19. Raise and support vehicle. Remove wheels and brake drums.
    Ensure right and left automatic adjuster lever and cable are properly
    connected.

20. Insert Brake Shoe Adjustment Gauge (J-21177-01) in drum.
    See Fig. 4. Expand gauge until inner legs contact drum braking
    surface. Lock gauge in position.

Fig. 4: Measuring Brake Drum Diameter Courtesy of Chrysler Motors.

21. Reverse brake shoe adjustment gauge, and install it on
    brake shoes. See Fig. 5. Position gauge legs at shoe centers. If gauge
    does not fit (too loose or too tight), adjust brake shoes accordingly.

22. Turn star adjuster wheel (by hand) to expand or retract
    brake shoes. Continue adjustment until gauge outside legs have a
    slight drag on shoes. Repeat procedure on opposite brake shoe

assembly.

5) Install brake drum and wheels. Lower vehicle. Make final adjustment by driving vehicle and making one forward stop (complete stop), followed by one reverse stop (complete stop). Repeat procedure 8-10 times to operate automatic adjusters and equalize adjustment.

Fig. 5: Measuring Brake Shoe Diameter Courtesy of Chrysler Motors.

STOPLIGHT SWITCH

Move brake pedal forward by hand until free play is taken up. If clearance between stoplight switch plunger and brake pedal is 1/8" (3 mm) and stoplight functions properly, no adjustment is needed. If adjustment is necessary, press brake pedal forward by hand. Push stoplight switch forward in mounting bracket as far as possible. Grasp brake pedal and pull rearward to stop and release. Recheck clearance and stoplight operation.

TESTING

POWER BOOSTER

Master Cylinder/Power Booster

23. Start engine, and check power booster vacuum hose for
    leaks. Repair as required. Stop engine, and place gear selector in
    Neutral. Pump brake pedal until all vacuum reserve is depleted.

24. Press and hold brake pedal under light foot pressure. If
    pedal does not hold firm and falls away, master cylinder is leaking
    internally. Repair or replace as required. If brake pedal holds firm,
    proceed to next step.

25. While holding light pressure on pedal, start engine, and
    note pedal action. If no pedal action is noticeable, power booster or
    vacuum check valve is faulty. Replace check valve, and repeat test. If
    pedal falls away slightly then holds firm, proceed to next step.

26. Release brake pedal. Increase engine speed to 1500 RPM,
    close throttle and immediately stop engine. Wait at least 90 seconds
    and retest pedal action. Booster should provide 2 or more vacuum
    assisted pedal applications. If pedal action is not as specified,
    perform CHECK VALVE & POWER BOOSTER VACUUM test.

Check Valve & Power Booster Vacuum

27. Disconnect vacuum hose from check valve. Remove check
    valve and seal from booster. Using a hand-held vacuum pump, apply 15-
    20 in. Hg at large end of check valve. If gauge on pump indicates any
    vacuum loss, valve is faulty and must be replaced. If gauge holds
    steadily, proceed to next step.

28. Reinstall check valve and seal into power booster. Tee a
    vacuum gauge into vacuum hose between power booster and vacuum source.
    Start engine, and let idle one minute. Clamp hose shut between vacuum
    source and power booster.

29. Stop engine, and observe vacuum gauge. If vacuum drops
    more than one in. Hg within 15 seconds, booster diaphragm or check
    valve is faulty. Replace as required.

BRAKE WARNING LIGHT SYSTEM

Electrical Circuit

Disconnect wire from switch terminal, and ground wire to chassis. Turn ignition on. Warning light should come on. If light does not operate, bulb or wiring circuit is defective. Replace bulb or repair wiring as necessary. If light illuminates, turn off ignition, and connect wire.

Warning Light Switch

30. Attach a bleeder hose to bleeder valve at either rear
    brake. Immerse other end of hose in container with brake fluid. Turn
    ignition on.

31. Open bleeder valve while pressure is being applied to
    brake pedal. Warning light should activate. Close bleeder valve before
    pressure is released from pedal.

32. Reapply brake pedal using moderate to heavy pressure.
    Light should go out. Repeat test on front brake system. System should
    function in same manner. Turn ignition off.

33. If light does not operate as specified for either system
    but comes on when electrical circuit is tested, warning light switch
    portion of valve is defective.

REMOVAL & INSTALLATION

FRONT BRAKE CALIPER & BRAKE PADS

NOTE: Replace brake pads when lining is 1/32" (.8 mm) from rivet heads.

Removal

34. Drain about half of brake fluid from master cylinder
    reservoir. Raise and support vehicle. Remove front wheels.

35. Place "C" clamp on caliper. Solid end of clamp should
    contact back of caliper. Screw end should contact metal part of
    outboard pad. Tighten "C" clamp until piston is forced to bottom of
    bore.

36. On 4WD models, do not allow "C" clamp screw to bear
    directly on outboard shoe retainer spring. If necessary, use wood or
    metal spacer between pad and "C" clamp screw.

37. On all models, remove caliper mounting pins. Lift caliper
    off rotor and anchor plate. On 4WD models, brake pads will remain
    attached to caliper. On 2WD models, brake pads will remain on caliper
    support.

38. On 4WD models, remove outboard pad. Press one end of
    outboard pad inward to disengage pad lug, and rotate shoe outward
    until retainer spring clears caliper. Press opposite end of pad inward
    to disengage opposite pad lug, and rotate pad up and out of caliper.
    To remove inboard pad, grasp ends of pad, and tilt pad outward to
    release springs from caliper piston. Remove pad from piston.

39. On 2WD models, hold lower anti-rattle clip against support
    bracket and remove outboard brake pad from caliper support. Remove
    inboard brake pad and both anti-rattle clips from caliper support.

40. On all models, disconnect brakeline at caliper, and cap
    hole to prevent contamination while removing caliper from vehicle.

Installation

41. To install, reverse removal procedure. Apply a light coat
    of multipurpose grease to caliper sliding surfaces. Lubricate caliper
    mounting pins and bushings with silicone.

42. Torque caliper mounting pins to specification. See, at the
    end of this article, TORQUE SPECIFICATIONS. Add brake fluid to
    reservoir. Apply brakes until brake pedal is firm. Check brake fluid
    level.

ROTOR

NOTE: DO NOT disconnect brake hose from caliper unless caliper is to be disassembled.

Removal (2WD)

43. Raise and support vehicle. Remove front wheels. Remove
    caliper. See FRONT BRAKE CALIPER & BRAKE PADS under REMOVAL &
    INSTALLATION. Suspend caliper from frame or suspension with wire.

44. Remove cap, cotter pin, nut retainer, adjusting nut and
    front bearing from spindle. Remove rotor from spindle. Remove grease
    seal and rear bearing from hub.

Installation (2WD)

45. Clean, inspect and repack wheel bearings. Replace grease
    seal. Coat spindle, bearing races and rotor hub cavity with grease.
    Clean rotor surface as required.

46. To install, reverse removal procedure. Tighten spindle nut
    to specification while rotating rotor to seat bearings. See, at the
    end of this article, TORQUE SPECIFICATIONS. Apply brakes until brake
    pedal is firm. Check brake fluid level.

Removal & Installation (4WD)

Raise and support vehicle. Remove front wheels. Remove caliper. See, under REMOVAL & INSTALLATION, FRONT BRAKE CALIPER & BRAKE PADS. Suspend caliper from frame or suspension. Remove retainers securing rotor to hub. Remove rotor from hub. To install, reverse removal procedure. See Fig. 6.

92D21835

Fig. 6: Exploded View Of Rotor & Hub Assembly Courtesy of Chrysler Motors.

REAR BRAKE SHOES

Removal

47. Raise and support vehicle. Remove wheels and brake drum.
    Remove "U" clip and washer from parking brake lever pivot pin. Place
    Wheel Cylinder Clamp (J-8002) over wheel cylinder.

48. Remove primary and secondary shoe return springs, hold-
    down spring and retainers and pins. See Fig. 7 or 8. Remove self-
    adjuster lever, adjuster and adjuster spring from brake shoes.

49. Remove brake shoes. Disconnect parking brake cable from
    parking brake lever, and remove lever.

50. 
    Shoe Return Springs

51. Cable Guide

52. Adjuster Lever

53. Adjuster Cable

54. Hold-Down Spring & Retainers

55. Secondary Shoe

56. Wheel Cylinder-To-Backing
    Plate Seal

57. Hold-Down Pins

9. Access Plug
10. Backing Plate

58. Cable Hole Plug

59. Parking Brake Strut & Spring

60. Self-Adjuster Assembly

61. Hold-Down Spring
    & Retainers

62. Primary Shoe

63. Shoe Guide Plate

64. Pin

65. Shoe Spring

66. Parking Brake Lever

_{LEFT REAR BRAKE ASSEMBLY}

cable. Using Brake Shoe Adjustment Gauge (J-21177-01), preset brake shoe adjustment. See REAR BRAKE SHOES under ADJUSTMENTS. Install brake drums. Install wheels, and lower vehicle. Check brake fluid. Road test vehicle.

OVERHAUL

NOTE: For overhaul, refer to appropriate illustration for exploded view of component. See Fig. 9 or 10.

CALIPER

Fig. 9: Exploded View Of Caliper Assembly Courtesy of Chrysler Motors.

MASTER CYLINDER

NOTE:

On vehicles with Anti-Lock Brake System (ABS), manufacturer does not recommend overhaul of master cylinder. If defective, replace master cylinder and power brake booster as an assembly.

Application In. (mm)

Disc Diameter 11.02 (279.9)

Lateral Runout

Cherokee & Wrangler 003 (.08)

Grand Cherokee & Grand Wagoneer 005 (. 13)

Parallelism 0005 (.013)

Original Thickness (1)

Minimum Refinish Thickness

Cherokee

2WD 86 (22)

4WD 89 (23)

All Others 89 (23)

(1) - Information is not available.

DRUM BRAKE SPECIFICATIONS

DRUM BRAKE SPECIFICATIONS TABLE

Application In. (mm)

Drum Diameter

Cherokee & Wrangler 9.00 (228.6)

Grand Cherokee & Grand Wagoneer (1)

Drum Width ( 1)

Maximum Drum Refinish Diameter

Cherokee & Wrangler 9.050 (230.00)

Grand Cherokee & Grand Wagoneer (1)

Wheel Cylinder Diameter (1)

Master Cylinder Diameter (1)

(1) - Information is not available.