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Disc Brake System Diagnosis

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: This diagnostic table is designed to diagnose only the components of the disc brake system in order to determine if the disc brake system is operating properly.
  1. Were you sent here from a brake symptom? If so, proceed to next step. If not, see DIAGNOSTIC STARTING POINT  .
  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, proceed 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, proceed 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, proceed 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, proceed 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. When complete, go to step  12 .
    7. CAUTION: Support the brake caliper with heavy mechanic's wire, or equivalent, whenever it is separated from its 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.
  7. 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. Inspect the disc brake caliper mounting bracket and the mounting/sliding hardware for the following conditions:
    • Loose, bent, cracked, or damaged caliper mounting bracket.
    • Binding or seized hardware.
    • Worn, damaged or missing hardware components.
    See DISC BRAKE MOUNTING & HARDWARE INSPECTION  under ADJUSTMENTS & INSPECTION. Replace components as required. See BRAKE CALIPER MOUNTING PLATE  or DISC BRAKE HARDWARE  under REMOVAL & INSTALLATION. Replace the unevenly-worn, loose or damaged disc brake pads as a complete axle set. See BRAKE PADS  under REMOVAL & INSTALLATION. When complete, 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 not, proceed to next step.
    9. CAUTION: Lubricant leaks from non-brake system components may come in contact with and contaminate brake system components.
  9. Inspect the rear axle seals for damage and evidence of a lubricant leak. Replace any rear axle seal that is found to be leaking lubricant which may be the source of the contamination to the pads. See appropriate RING GEARS article in DRIVELINE/AXLES. Did you find and correct the source of the leak causing contamination of the pads? If so, go to step  11 . If not, proceed to next step.
    10. CAUTION: Lubricant leaks from non-brake system components may come in contact with and contaminate brake system components.
  10. Inspect the following systems for damage and evidence of an external fluid leak. Replace any components found to be leaking fluid which may be the source of the contamination to the pads. Refer to the following:
    • DIAGNOSTIC in appropriate POWER RECIRCULATING BALL article IN STEERING.
    • TROUBLESHOOTING in appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSION.
    When the source of the leak causing contamination of the pads has been found and corrected, proceed to next step.
    11. CAUTION: Support the brake caliper with heavy mechanic's wire, or equivalent, whenever it is separated from its 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.
  11. Clean the remaining disc brake system components to remove any traces of the contaminant. 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. Inspect the disc brake caliper mounting/sliding hardware for binding or seized hardware and distorted, worn, damaged or missing hardware components. See DISC BRAKE MOUNTING & HARDWARE INSPECTION  under REMOVAL & INSTALLATION. Replace the caliper mounting/sliding hardware components as required. See DISC BRAKE HARDWARE  under REMOVAL & INSTALLATION. Replace the contaminated disc brake pads as a complete axle set. See BRAKE PADS  under REMOVAL & INSTALLATION. When complete, proceed to next step.
    12. CAUTION: Disc brake rotor shields/backing plates that come in contact with disc brake rotors may cause brake system noise.
  12. Visually inspect each of the disc brake rotor shields/backing plates for evidence of contact with the brake rotors. Are any of the brake rotor shields/backing plates contacting the brake rotors? If so, proceed to next step. If not, go to step  14 .
  13. Repair or replace the disc brake rotor shields/backing plates as required. See FRONT DISC BRAKE SPLASH SHIELD  or REAR DISC BRAKE BACKING PLATE  under REMOVAL & INSTALLATION. When complete, proceed to next step.
    14. NOTE: Make the following determination and answer the question individually for each rotor.
  14. 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 ADJUSTMENTS & INSPECTION. Does the disc brake rotor meet the minimum requirements for refinishing? If so, proceed to next step. If not, go to step  17 .
  15. Inspect each of the disc brake rotors for the following surface and wear conditions:

    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.
    See BRAKE ROTOR SURFACE & WEAR INSPECTION  in ADJUSTMENTS & INSPECTION. 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, proceed to next step. If not, go to step  20 .
  16. Refinish the brake rotor. See BRAKE ROTOR REFINISHING  under SERVICING. Inspect the brake rotor thickness. See BRAKE ROTOR THICKNESS MEASUREMENT  under ADJUSTMENTS & INSPECTION. Were you able to refinish the brake rotor within the minimum requirements? If so, go to step  20 . If not, go to step  19 .
  17. Is the brake rotor at or below the discard requirements? If so, go to step  19 . If not, proceed to next step.
  18. Inspect each of the disc brake rotors for the following surface and wear conditions:

    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.
    See BRAKE ROTOR SURFACE & WEAR INSPECTION  in ADJUSTMENTS & INSPECTION. 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, proceed to next step. If not, go to step  20 .
  19. Replace the brake rotor. See BRAKE ROTOR  under REMOVAL & INSTALLATION. When replacement is complete, proceed to next step.
  20. Install or connect components that were removed or disconnected during diagnosis. When complete, disc brake system okay.
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