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Drum 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. Remove the brake drums. See BRAKE DRUM  under REMOVAL & INSTALLATION. Inspect the drum brake shoes for the following conditions:
    • Lining thickness below specifications.
    • Uneven and/or abnormal wear - edge-to-edge and/or side-to-side.
    • Contamination from an external substance.
    • Looseness, damage, glazing, or incorrect lining material.

    Did you find any conditions to indicate a concern with any of the drum brake shoes? If so, go to next step. If not, go to step  7.

  3. Are any of the brake shoes contaminated? If so, go to next step. If not, go to step  5.
  4. Inspect the wheel cylinders for evidence of an external brake fluid leak. Replace any wheel cylinder that is found to be leaking brake fluid. See WHEEL CYLINDER  under REMOVAL & INSTALLATION. After completing the inspection and replacement, go to step  6.
  5. Inspect the drum brake hardware for any components which are worn, damaged, discolored due to stress, broken or missing. See DRUM BRAKE HARDWARE INSPECTION  under ADJUSTMENTS & INSPECTION. Replace components as required. See BRAKE HARDWARE  under REMOVAL & INSTALLATION. Replace the drum brake shoes. See BRAKE SHOE  under REMOVAL & INSTALLATION. After completing the inspection and replacement, go to step  8.
  6. Clean the remaining drum brake system components to remove any traces of the contaminant. Inspect the drum brake hardware for any components which are worn, damaged, discolored due to stress, broken or missing. See DRUM BRAKE HARDWARE INSPECTION  under ADJUSTMENTS & INSPECTION. Replace the drum brake hardware components as required. See BRAKE HARDWARE  under REMOVAL & INSTALLATION. Replace the contaminated brake shoes. See BRAKE SHOE  under REMOVAL & INSTALLATION. After completing the cleaning, inspection and replacement, go to step  8.
  7. Inspect the drum brake hardware for any components which are worn, damaged, discolored due to stress, broken or missing. See DRUM BRAKE HARDWARE INSPECTION  under ADJUSTMENTS & INSPECTION. Replace components as required. See BRAKE HARDWARE  under REMOVAL & INSTALLATION. After completing the inspection and, if necessary, the replacement, go to next step.
  8. Check the diameter of each of the brake drums. Make a determination for each brake drum if the drum can be REFINISHED and REMAIN ABOVE the minimum requirements. See BRAKE DRUM DIAMETER MEASUREMENT  under REAR DRUM BRAKE in ADJUSTMENTS & INSPECTION. Does the brake drum meet the minimum requirements for REFINISHING? If so, go to next step. If not, go to step  11.
    1. Inspect each of the brake drums for the following surface and wear conditions: See BRAKE DRUM SURFACE & WEAR INSPECTION  under REAR DRUM BRAKE in ADJUSTMENTS & INSPECTION.

      Braking Surface Conditions

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

      Braking Surface Wear Conditions

      • Deep or excessive scoring beyond maximum acceptable level.
      • Radial runout beyond maximum acceptable level.
    2. Make a determination for each brake drum if the drum requires refinishing based upon the results of the inspection. If the brake drum exhibits any of the following conditions, it requires refinishing.
      • Drum exhibits one or more of the Braking Surface Conditions listed previously.
      • Drum is beyond the acceptable level in one or more of the Braking Surface Wear Conditions listed previously
    Does the brake drum require REFINISHING? If so, go to next step. If not, go to step  14.
  10. Refinish the brake drum. See BRAKE DRUM REFINISHING  under SERVICING. Inspect the brake drum diameter. See BRAKE DRUM DIAMETER MEASUREMENT  under REAR DRUM BRAKE in ADJUSTMENTS & INSPECTION. Were you able to REFINISH the brake drum within the minimum requirements? If so, go to step  14. If not, go to step  13.
  11. Is the brake drum at or below the DISCARD requirements? If so, go to step  13. If not, go to next step.
    1. Inspect each of the brake drums for the following surface and wear conditions: See BRAKE DRUM SURFACE & WEAR INSPECTION  under REAR DRUM BRAKE in ADJUSTMENTS & INSPECTION.

      Braking Surface Conditions

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

      Braking Surface Wear Conditions

      • Deep or excessive scoring beyond maximum acceptable level
      • Radial runout beyond maximum acceptable level
    2. Make a determination for each brake drum if the drum requires replacement based upon the results of the inspection. If a brake drum exhibits any of the following conditions, it requires replacement.
      • Drum exhibits one or more of the Braking Surface Conditions listed previously
      • Drum is beyond the acceptable level in one or more of the Braking Surface Wear Conditions listed previously
    Does the brake drum require REPLACEMENT? If so, go to next step. If not, go to step  14.
  13. Replace the brake drum. See BRAKE DRUM  under REMOVAL & INSTALLATION. After completing the replacement, go to next step.
  14. Inspect the brake shoes for proper adjustment. See DRUM BRAKE ADJUSTMENT  under REAR DRUM BRAKE in ADJUSTMENTS & INSPECTION. Are the brake shoes adjusted properly? If so, go to step  18. If not, go to next step.
  15. Inspect the components of the brake drum adjustment hardware system for free movement and correct operation. See DRUM BRAKE ADJUSTING HARDWARE INSPECTION  under REAR DRUM BRAKE in ADJUSTMENTS & INSPECTION. Do the drum brake adjusting hardware components operate freely and correctly? If so, go to step  17. If not, go to next step.
  16. Replace the drum brake adjusting hardware components as necessary. See DRUM BRAKE ADJUSTING HARDWARE INSPECTION  under REAR DRUM BRAKE in ADJUSTMENTS & INSPECTION. After completing the replacement, go to next step.
  17. Adjust the drum brake shoes. See DRUM BRAKE ADJUSTMENT  under REAR DRUM BRAKE in ADJUSTMENTS & INSPECTION. Were you able to complete the adjustment? If so, go to step  20. If not, then return to the symptom table. See SYMPTOM LIST  under GENERAL DIAGNOSIS in TROUBLE SHOOTING.
  18. Inspect the drum brake backing plate for the following:
    • Excessive wear or rust.
    • Damage and/or evidence of contact with the brake drum.

    Does the drum brake backing plate exhibit any of these conditions? If so, go to next step. If not, the go to step  20.

  19. Repair or replace the drum brake backing plate as necessary. See BRAKE BAKING PLATE  under REMOVAL & INSTALLATION. After completing the repair or replacement, go to next step.
  20. Install or connect components that were removed or disconnected during diagnosis. After completing the operation, the system should be okay.
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