GM Cadillac 1967-1989 Repair Guide

Component Replacement

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CHECKING AND ADDING BRAKE FLUID



Do not use any brake fluid which may contain a petroleum base. Do not use a container which has been used for petroleum based fluids or a container which is wet with water. Petroleum based fluids will cause swelling and distortion of rubber parts in the hydraulic brake system and water will mix with brake fluid, lowering the fluid boiling point. Keep all fluid containers capped to prevent contamination.

The plastic fluid reservoir, on the ABS hydraulic unit, has a label marking the proper "FULL" level. The hydraulic accumulator must be depressurized when checking the brake fluid level. Use the following procedure to check the brake fluid level.

  1. With the ignition switch OFF , depressurize the hydraulic accumulator by applying the brake pedal approximately 25 times using a pedal force of approximately 50 lbs. (222 N). A noticeable change in the pedal feel will occur when the accumulator is depressurized. Continue to apply the pedal several times after this change in pedal feel occurs.
  2.  
  3. Inspect the fluid level.
  4.  
  5. Thoroughly clean the reservoir cap and surrounding area prior to cap removal to avoid contamination of the reservoir.
  6.  
  7. Fill the reservoir to the "FULL" mark using DOT-3 brake fluid. Use of DOT-5 silicone fluid is not allowed, as internal damage to the pump components may result.
  8.  

BLEEDING BRAKE SYSTEM



Pressure Bleeding

See Figure 1 FRONT BRAKES

  1. With the ignition OFF , depressurize the hydraulic accumulator by pumping the brake pedal a minimum of 25 times using a pedal force of approximately 50 lbs. (222 N).
  2.  
  3. Remove the reservoir cap.
  4.  
  5. Install the pressure bleeder adapter J-35789 or equivalent.
  6.  
  7. Attach the bleeder equipment to bleeder adapter. Charge the pressure bleeder to approximately 20 psi (138 kPa).
  8.  
  9. Connect a transparent hose to either front caliper bleed screw. Submerge the free end of the hose in a clear glass container which is partially filled with clean brake fluid.
  10.  
  11. With the pressure bleeder turned on, open the caliper bleed screw 1 / 2 - 3 / 4 turn and allow the fluid to flow into the container. Leave the caliper bleed screw open until clear, bubble-free fluid flows from the hose.
  12.  
  13. Repeat Step 6 at the other front caliper.
  14.  
  15. After bleeding at both front calipers, remove the pressure bleeding equipment and bleeder adapter.
  16.  
  17. Remove excess brake fluid from the reservoir to bring the fluid level to the "FULL" mark.
  18.  

Do not remove brake fluid from the reservoir using a syringe or other instrument which is contaminated with water, petroleum based fluids or any other foreign material. Contamination of the brake fluid may result in impaired system operation, property damage or personal injury.

  1. Install the reservoir cap. Turn the ignition ON and allow the pump to charge the accumulator.
  2.  



Click image to see an enlarged view

Fig. Fig. 1: Pressure bleeding - Anti-Lock Brake System

REAR BRAKES
  1. Turn the ignition ON and allow the system to charge. (The pump motor will stop when the system is charged.)
  2.  
  3. Attach a bleeder hose to 1 rear bleeder valve. Submerge the other end of the hose in a container of clean brake fluid.
  4.  
  5. With the ignition ON , have an assistant slightly depress the brake pedal and hold it.
  6.  
  7. Open the caliper bleed screw 1 / 2 - 3 / 4 turn and allow brake fluid to flow into the container. Leave the caliper bleed screw open until it is clear, bubble-free fluid flows from the hose.
  8.  
  9. When air-free brake fluid flows from the bleeder hose, close the caliper bleed screw.
  10.  
  11. Check the brake fluid level periodically during the bleeding procedure. Do not allow the fluid level to drop below the reservoir seam line.
  12.  
  13. Repeat Steps 2-5 on the other rear bleeder valve.
  14.  
  15. After bleeding is completed, depressurize the accumulator and fill the fluid reservoir to the "FULL" mark.
  16.  


CAUTION
Do not move the vehicle until a firm brake pedal is obtained. Failure to obtain a firm brake pedal may result in a brake system failure and personal injury.

Manual Bleeding

The front hydraulic system may be manually bled using conventional bleeding methods. The rear brakes can not be bled using conventional methods and should be pressure bled.

  1. With the ignition OFF , depressurize the hydraulic accumulator by pumping the brake pedal a minimum of 25 times using a pedal force of approximately 50 lbs. (222 N).
  2.  


CAUTION
Failure to depressurize the hydraulic accumulator, prior to performing this operation may result in personal injury and/or damage to the painted surfaces!

  1. Connect a transparent hose to the caliper bleed screw. Submerge the free end of the hose in a clear glass container, which is partially filled with clean, fresh brake fluid.
  2.  
  3. Slowly pump the brake pedal several times, using full strokes of the pedal and allowing approximately 5 seconds between pedal strokes. After 2 or 3 strokes, continue to hold pressure on the pedal, keeping it at the bottom of its travel.
  4.  
  5. With pressure on the pedal, open the bleed screw 1 / 2 - 3 / 4 turn. Leave bleed screw open until fluid no longer flows from the hose. Tighten the bleed screw and release the pedal.
  6.  
  7. Repeat this procedure until clear, bubble-free fluid flows from the hose.
  8.  
  9. Repeat all steps at each of the calipers.
  10.  

ADJUSTMENT



Front Wheel Speed Sensor
  1. Loosen the front wheel speed sensor mounting bracket bolts so that the bracket is snug to the knuckle but can be moved by hand.
  2.  
  3. Using a feeler gauge, adjust the sensor (between the tip of the sensor and one of the teeth on the toothed sensor ring) to 0.020 in. (0.50mm) by moving the bracket.
  4.  
  5. Tighten the mounting bracket bolts to 19 ft. lbs. (26 Nm).
  6.  
  7. After tightening the bolts, check the sensor gap to be sure that it was not disturbed while tightening the bracket bolts.
  8.  

REMOVAL & INSTALLATION



Hydraulic Unit

See Figure 2

  1. Disconnect the negative battery cable.
  2.  
  3. Depressurize the accumulator by applying and releasing the brake pedal a minimum of 25 times using approximately 50 lbs. (222 N) force on the pedal. A noticeable change in pedal feel will occur when the accumulator is completely discharged.
  4.  
  5. Label and disconnect all electrical connections to the unit.
  6.  
  7. Remove the pump bolt and move the energy unit to the side to gain access to the brake lines.
  8.  
  9. Disconnect the 3 lines connected to the valve block. Use a second wrench to prevent the line from twisting.
  10.  
  11. Disconnect the line attaching the hydraulic unit to the combination valve.
  12.  
  13. From the inside of the car, disconnect the pushrod from the brake pedal.
  14.  
  15. Push the dust boot forward, past the hex on the pushrod.
  16.  
  17. Separate the pushrod halves by unthreading the 2 pieces.
  18.  
  19. Remove the 2 unit-to-pushrod bracket bolts and remove the hydraulic unit.
  20.  

The front half of the pushrod will remain locked into the hydraulic unit.

To install:
  1. Position the hydraulic unit to the support bracket.
  2.  
  3. Install the support bracket bolts and torque them to 37 ft. lbs. (50 Nm).
  4.  
  5. Thread the 2 halves of the pushrod together and tighten.
  6.  
  7. Reposition the dust boot.
  8.  
  9. Connect the line from the combination valve to the hydraulic unit.
  10.  
  11. Connect the 3 lines to the valve block, reposition the energy unit as necessary.
  12.  
  13. Install all the electrical connections to the unit.
  14.  
  15. Connect the negative battery cable.
  16.  
  17. Bleed the brake system.
  18.  



Click image to see an enlarged view

Fig. Fig. 2: Hydraulic unit mounting - Anti-Lock Brake System

Pump and Motor Assembly

See Figure 3

  1. Disconnect the negative battery cable.
  2.  
  3. Depressurize the accumulator by applying and releasing the brake pedal a minimum of 25 times using approximately 50 lbs. (222 N) force on the pedal. A noticeable change in pedal feel will occur when the accumulator is completely discharged.
  4.  
  5. Disconnect the electrical connector from the pressure switch and the electric motor. Remove the fluid from the reservoir.
  6.  

Do not remove brake fluid from the reservoir using a syringe or other instrument which is contaminated with water, petroleum based fluids or any other foreign material. Contamination of the brake fluid may result in impaired system operation, property damage or personal injury.

  1. Remove the hydraulic accumulator and O-ring.
  2.  
  3. Disconnect the high pressure hose fitting connected to the pump.
  4.  
  5. Remove the pressure hose assembly and O-rings.
  6.  
  7. Disconnect the wire clip then, pull the return hose fitting out of the pump body.
  8.  
  9. Remove the bolt attaching the pump and motor assembly to the main body.
  10.  
  11. Remove the pump and motor assembly by sliding it off of the locating pin.
  12.  

Replace the insulators if damaged or deteriorated.

To install:
  1. Position the pump and motor assembly to the main body.
  2.  
  3. Install the bolt attaching the pump and motor assembly to the main body.
  4.  
  5. Connect the pressure hose assembly.
  6.  
  7. Connect the return hose and fitting into the pump body. Install the wire clip.
  8.  
  9. Install the bolt, O-rings and fitting of the high pressure hose to the pump assembly.
  10.  
  11. Connect the electrical connector to the pump motor.
  12.  
  13. Connect the negative battery cable.
  14.  



Click image to see an enlarged view

Fig. Fig. 3: Pump assembly components - Anti-Lock Brake System

Valve Block Assembly

See Figure 4

  1. Disconnect the negative battery cable.
  2.  
  3. Depressurize the accumulator by applying and releasing the brake pedal a minimum of 25 times using approximately 50 lbs. (222 N) force on the pedal. A noticeable change in pedal feel will occur when the accumulator is completely discharged.
  4.  
  5. Remove the hydraulic unit.
  6.  
  7. Remove the 3 nuts and washers.
  8.  
  9. Remove the valve block assembly and O-rings by sliding the valve block off of the studs.
  10.  

To install:
  1. Lubricate the O-rings with brake fluid.
  2.  
  3. Install the valve block and O-rings onto the master cylinder body.
  4.  
  5. Install the 3 nuts and washers removed in Step 4.
  6.  
  7. Install the hydraulic unit.
  8.  
  9. Install the negative battery cable.
  10.  
  11. Refill and bleed the system.
  12.  



Click image to see an enlarged view

Fig. Fig. 4: Valve block removal - Anti-Lock Brake System

Pressure Warning Switch
  1. Disconnect the negative battery cable.
  2.  
  3. Depressurize the accumulator by applying and releasing the brake pedal a minimum of 25 times using approximately 50 lbs. (222 N) force on the pedal. A noticeable change in pedal feel will occur when the accumulator is completely discharged.
  4.  
  5. Disconnect the electrical connector from the pressure/warning switch.
  6.  
  7. Remove the pressure/warning switch using special tool No. J-35804.
  8.  
  9. Remove the O-ring from the switch.
  10.  

To install:
  1. Lubricate the O-ring with clean brake fluid.
  2.  
  3. Install the O-ring on the pressure/warning switch.
  4.  
  5. Install the switch and tighten to 15 ft. lbs. (20 Nm) using special tool No. J-35804.
  6.  
  7. Connect the electrical connector to the pressure/warning switch.
  8.  
  9. Connect the negative battery cable.
  10.  
  11. Turn the ignition to the ON position. The "Brake" light should go out within 30 seconds and the pump motor should turn off within 40 seconds.
  12.  
  13. Check for leakage around the switch.
  14.  

Hydraulic Accumulator

  1. Disconnect the negative battery cable.
  2.  
  3. Depressurize the accumulator by applying and releasing the brake pedal a minimum of 25 times using approximately 50 lbs. (222 N) force on the pedal. A noticeable change in pedal feel will occur when the accumulator is completely discharged.
  4.  
  5. Unscrew the hydraulic accumulator from the hydraulic unit.
  6.  
  7. Remove the O-ring from the accumulator.
  8.  

To install:
  1. Lubricate a new O-ring with clean brake fluid and install it on the accumulator.
  2.  
  3. Install the accumulator and tighten to 30 ft. lbs. (40 Nm).
  4.  
  5. Connect the negative battery cable.
  6.  
  7. Turn the ignition to the ON position. The "Brake" light should go out within 30 seconds and the pump motor should turn off within 40 seconds.
  8.  
  9. Check for leakage around the accumulator.
  10.  

Brake Fluid Reservoir and Seal

  1. Disconnect the negative battery cable.
  2.  
  3. Depressurize the accumulator by applying and releasing the brake pedal a minimum of 25 times using approximately 50 lbs. (222 N) force on the pedal. A noticeable change in pedal feel will occur when the accumulator is completely discharged.
  4.  
  5. Remove the return hose and drain the brake fluid into a container and discard the fluid.
  6.  
  7. Disconnect the electrical connectors from the fluid level sensor assembly.
  8.  
  9. Remove the reservoir to block mounting bolt.
  10.  
  11. Remove the reservoir by carefully prying between the reservoir and the master cylinder.
  12.  

To install:
  1. Lubricate the seals with clean brake fluid.
  2.  
  3. Install the seals and O-ring into the master cylinder body.
  4.  
  5. Push the reservoir into the master cylinder until it is fully seated.
  6.  
  7. Install the reservoir to valve block mounting bracket bolt.
  8.  
  9. Connect the electrical connectors to the reservoir cap.
  10.  
  11. Connect the sump hose to the reservoir.
  12.  
  13. Refill the reservoir with clean brake fluid.
  14.  
  15. Connect the negative battery cable.
  16.  

Wheel Speed SensorFRONT

See Figure 5

  1. Disconnect the sensor connector from the underhood area near the strut tower.
  2.  
  3. Raise the vehicle and support on safety stands.
  4.  
  5. Disengage the sensor cable grommet from the wheel house pass-through hose and remove the sensor cable from the retaining brackets.
  6.  
  7. To remove the sensor (without the mounting bracket):
    1. Remove the sensor mounting bolt.
    2.  
    3. Remove the sensor from the vehicle.
    4.  

  8.  
  9. To remove the sensor (with the mounting bracket):
    1. Remove the mounting bracket bolts.
    2.  
    3. Remove the assembly from the vehicle.
    4.  
    5. If necessary, remove the sensor from the mounting bracket.
    6.  

  10.  

To install:
  1. If the mounting bracket was removed from the knuckle, install the mounting bracket and bolts. Install the bracket bolts finger tight. Do not tighten at this time.
  2.  
  3. If the sensor was removed from the mounting bracket, thoroughly coat the sensor with anti-corrosion compound (GM P/N 1052856) or equivalent in all areas where the sensor contacts the mounting bracket. Install the sensor in the mounting bracket and tighten to 9 ft. lbs. (12 Nm).
  4.  

Failure to coat the sensor with anti-corrosion compound prior to installation in the bracket will result in reduced sensor life.

  1. Route the sensor cable and install in the retainers. Install the wheelhouse pass-through grommet.
  2.  

Proper installation of the wheel speed sensor cables is critical to continued system operation. Be sure that the cables are installed in retainers. Failure to install the cables in the retainers may result in contact with moving parts and/or over-extension of the cables, resulting in circuit damage.

  1. If the mounting bracket was loosened or removed, adjust the front sensor gap.
  2.  
  3. Lower the vehicle.
  4.  
  5. Connect the wheel speed sensor connector underhood.
  6.  



Click image to see an enlarged view

Fig. Fig. 5: Front wheel speed sensor - Anti-Lock Brake System

REAR

See Figure 6

  1. Raise the vehicle and support on safety stands.
  2.  
  3. Disconnect the sensor connector and remove the sensor cable from the retainer brackets.
  4.  
  5. Remove the sensor mounting bolt and remove the sensor from the vehicle.
  6.  

To install:
  1. Position the sensor in the knuckle and install the mounting bolt. Tighten mounting bolt to 9 ft. lbs. (12 Nm).
  2.  
  3. Install the wheel speed sensor cable in the retainers.
  4.  

Proper installation of the wheel speed sensor cables is critical to continued system operation. Be sure that the cables are installed in retainers. Failure to install the cables in the retainers may result in contact with moving parts and/or over-extension of the cables, resulting in circuit damage.

  1. Connect the wheel speed sensor connector.
  2.  



Click image to see an enlarged view

Fig. Fig. 6: Right rear wheel speed sensor, left side similar - Anti-Lock Brake System

 
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