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Disc Brake Diagnosis

WARNING: This page is about a different car, the 2003 Pontiac Aztek and 2003 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
  1. Were you sent here from a Symptom Test? If so, go to next step. If not, go to GENERAL DIAGNOSIS  under TROUBLE SHOOTING.
  2. Visually inspect the disc brake pads for the following:
    • Lining thickness.
    • Uneven and/or abnormal wear (edge-to-edge and/or side-to-side).
    • Evidence of contamination from an external substance.
    • Looseness or damage (including pad hardware).

    Did you find any conditions to indicate a concern with any of the (front and/or rear) disc brake pads? If so, go to next step. If not, go to step  12.

  3. Are any of the (front and/or rear) disc brake pads contaminated? If so, go to step  8. If not, go to next step.
  4. Are any of the (front and/or rear) disc brake pads worn unevenly? If so, go to step  7. If not, go to next step.
  5. Are any of the (front and/or rear) disc brake pads and/or pad hardware loose or damaged? If so, go to step  7. If not, go to next step.
  6. Remove and inspect the worn disc brake pads for glazing, looseness, heat spots or damage. Replace the worn disc brake pads as a complete axle set. See BRAKE PADS  under REMOVAL & INSTALLATION. After completing the inspection and replacement, go to step  12.
  7. Support the brake caliper with heavy mechanic's wire, or equivalent, whenever it is separated from it's mount and the hydraulic flexible brake hose is still connected. Failure to support the caliper in this manner will cause the flexible brake hose to bear the weight of the caliper, which may cause damage to the brake hose and in turn may cause a brake fluid leak.
    1. Remove the (front and/or rear) disc brake calipers (as appropriate) from the mounting brackets and support the calipers. DO NOT disconnect the hydraulic brake flex hoses from the calipers. See BRAKE CALIPER  under REMOVAL & INSTALLATION.
    2. Inspect the disc brake caliper mounting bracket and the mounting/sliding hardware for the following conditions: See FRONT DISC BRAKE MOUNTING & HARDWARE INSPECTION  and REAR DISC BRAKE MOUNTING & HARDWARE INSPECTION  , if equipped, under FRONT & REAR DISC BRAKE in ADJUSTMENTS & INSPECTION.
      • Loose, bent, cracked, or damaged caliper mounting bracket.
      • Binding or seized hardware.
      • Worn, damaged or missing hardware components.
    3. Replace components as required. Refer to the following procedures, as required:
    4. Replace the unevenly-worn, loose or damaged disc brake pads as a complete axle set. See BRAKE PADS  under REMOVAL & INSTALLATION.

    After completing the inspection and replacement, go to step  12.

  8. Inspect the disc brake calipers, brake hoses and brake pipes for evidence of an external brake fluid leak. Replace any components found to be leaking brake fluid. Refer to the following procedures as required:

    Did you find and correct the source of the leak causing contamination of the pads? If so, go to step  11. If no, go to next step.

  9. Inspect the wheel drive shaft outer seals (boots) for damage and evidence of a grease leak. Replace any wheel drive shaft seal (boot) that is found to be leaking grease which may be the source of the contamination to the pads. See appropriate AXLE SHAFTS article in DRIVELINES/AXLES. Did you find and correct the source of the leak causing contamination of the pads? If so, go to step  11. If not, go to next step.
  10. Inspect the following systems for damage and evidence of an external fluid leak and replace any components found to be leaking fluid which may be the source of the contamination to the pads. Refer to the following procedures:
    • For power steering leaks, see TROUBLE SHOOTING article in GENERAL INFORMATION.
    • For transmission leaks, See ON-VEHICLE REPAIRS in SERVICING - AZTEK & RENDEZVOUS article in TRANSMISSIONS.

    Did you find and correct the source of the leak causing contamination of the pads? If so, go to next step.

    1. Clean the remaining disc brake system components to remove any traces of the contaminant.
      2. NOTE: Support the brake caliper with heavy mechanic's wire, or equivalent, whenever it is separated from it's mount and the hydraulic flexible brake hose is still connected. Failure to support the caliper in this manner will cause the flexible brake hose to bear the weight of the caliper, which may cause damage to the brake hose and in turn may cause a brake fluid leak.
    2. Remove the (front and/or rear) disc brake calipers (as appropriate) from the mounting brackets and support the calipers. DO NOT disconnect the hydraulic brake flex hoses from the calipers. See BRAKE CALIPER  under REMOVAL & INSTALLATION.
    3. Inspect the disc brake caliper mounting/sliding hardware for the following conditions: See FRONT DISC BRAKE MOUNTING & HARDWARE INSPECTION  and REAR DISC BRAKE MOUNTING & HARDWARE INSPECTION  , if equipped, under FRONT & REAR DISC BRAKE in ADJUSTMENTS & INSPECTION.
      • Binding or seized hardware.
      • Distorted, worn, damaged or missing hardware components.
    4. Replace the caliper mounting/sliding hardware components as required. See BRAKE HARDWARE  under REMOVAL & INSTALLATION.
    5. Replace the contaminated disc brake pads as a complete axle set. See BRAKE PADS  under REMOVAL & INSTALLATION.
    After completing the cleaning, inspection and replacement, go to next step.
  12. Check the thickness of each of the disc brake rotors. Make a determination for each brake rotor if the rotor can be REFINISHED and REMAIN ABOVE the minimum requirements. See BRAKE ROTOR THICKNESS MEASUREMENT  under FRONT & REAR DISC BRAKE in ADJUSTMENTS & INSPECTION. Does the disc brake rotor meet the minimum requirements for REFINISHING? If so, go to next step. If not, go to step  15.
    • Inspect each of the disc brake rotors for the following surface and wear conditions: See BRAKE ROTOR SURFACE & WEAR INSPECTION  under FRONT & REAR DISC BRAKE in ADJUSTMENTS & INSPECTION.

      Braking Surface Conditions:

      • Heavy rust and/or pitting.
      • Cracks and/or heat spots.
      • Excessive blueing discoloration.

      Braking Surface Wear Conditions:

      • Deep or excessive scoring beyond maximum acceptable level.
      • Lateral runout beyond maximum acceptable level.
      • Thickness variation beyond maximum acceptable level.

      Make a determination for each brake rotor if the rotor requires refinishing based upon the results of the inspection. If the brake rotor exhibits any of the following conditions, it requires refinishing.

      • Rotor exhibits one or more of the Braking Surface Conditions listed previously.
      • Rotor is beyond the acceptable level in one or more of the Braking Surface Wear Conditions listed previously.

    Does the brake rotor require REFINISHING? If so, go to next step. If not, go to step  18.
    1. Refinish the brake rotor. See BRAKE ROTOR REFINISHING  under SERVICING.
    2. Inspect the brake rotor thickness. See BRAKE ROTOR THICKNESS MEASUREMENT  under FRONT & REAR DISC BRAKE in ADJUSTMENTS & INSPECTION.
    Were you able to REFINISH the brake rotor within the minimum requirements? If so, go to step  18. If not, go to step  17.
  15. Is the brake rotor at or below the DISCARD requirements? If so, go to step  17. If not, go to next step.
    1. Inspect each of the disc brake rotors for the following surface and wear conditions: See BRAKE ROTOR SURFACE & WEAR INSPECTION  under FRONT & REAR DISC BRAKE in ADJUSTMENTS & INSPECTION.

      Braking Surface Conditions

      • Heavy rust and/or pitting
      • Cracks and/or heat spots
      • Excessive blueing discoloration

      Braking Surface Wear Conditions

      • Deep or excessive scoring beyond maximum acceptable level
      • Lateral runout beyond maximum acceptable level
      • Thickness variation beyond maximum acceptable level
    2. Make a determination for each brake rotor if the rotor requires replacement based upon the results of the inspection. If a brake rotor exhibits any of the following conditions, it requires replacement.
      • Rotor exhibits one or more of the Braking Surface Conditions listed previously
      • Rotor is beyond the acceptable level in one or more of the Braking Surface Wear Conditions listed previously
    Does the brake rotor require REPLACEMENT? If so, go to next step. If not, go to step  18.
  17. Replace the brake rotor. See BRAKE ROTOR  under REMOVAL & INSTALLATION. After completing the replacement, go to next step.
  18. Install or connect components that were removed or disconnected during diagnosis. After completing the operation, the system should be okay.
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