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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 467 (Disc Brakes & Drum Brakes) >> Trouble Shooting >> General Diagnosis (Drum Brake) >> Drum Brake System Diagnosis

Drum Brake System Diagnosis

WARNING: This page is about a different car, the 2002 GMC Safari and 2002 Chevrolet Astro. However, it is still accessible from the selected car via links, so may be relevant.
  1. Were you sent here from a Brake Symptom Table? If so, go to next step. If not, see GENERAL DIAGNOSIS (HYDRAULIC BRAKES) .
  2. Remove brake drums. See REAR BRAKE DRUM . Inspect 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 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 . After completing inspection and replacement, go to step  6.
  5. Inspect drum brake hardware for any components which are worn, damaged, discolored due to stress, broken or missing. Replace components as necessary. See DRUM BRAKE HARDWARE . Replace drum brake shoes. See REAR BRAKE SHOES . After completing repair, go to step  8.
  6. Clean the remaining drum brake system components to remove any traces of the contaminant. Inspect drum brake hardware for any components which are worn, damaged, discolored due to stress, broken or missing. Replace drum brake hardware components as necessary. See DRUM BRAKE HARDWARE . Replace contaminated brake shoes. See REAR BRAKE SHOES . After completing repair, go to step  8.
  7. Inspect drum brake hardware for any components which are worn, damaged, discolored due to stress, broken or missing. Replace components as necessary. See DRUM BRAKE HARDWARE . After completing repair, go to next step.
  8. Check 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 DRUM BRAKE SPECIFICATIONS . Does the brake drum meet the minimum requirements for REFINISHING? If so, go to next step. If not, go to step  11.
  9. Inspect each of the brake drums for heavy rust and/or pitting, cracks and/or heat spots, or excessive blueing discoloration. Inspect for missing balance weights, deep or excessive scoring beyond maximum acceptable level, or radial runout beyond maximum acceptable level. Make a determination for each brake drum if the drum requires refinishing based upon the results of the inspection. If brake drum exhibits any of the conditions, it requires refinishing. If brake drum exhibits one or more of the conditions, drum wear is beyond acceptable level. Does the brake drum require refinishing? If so, go to the next step. If not, go to step  14.
  10. Refinish brake drum. Inspect brake drum diameter. See DRUM BRAKE SPECIFICATIONS . 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 not, go to next step. If so, go to step  13.
  12. Inspect each of the brake drums for heavy rust and/or pitting, cracks and/or heat spots, or excessive blueing discoloration. Inspect for missing balance weights, deep or excessive scoring beyond maximum acceptable level, or radial runout beyond maximum acceptable level. Make a determination for each brake drum if the drum requires refinishing based upon the results of the inspection. If brake drum exhibits any of the conditions, it requires refinishing. If brake drum exhibits one or more of the conditions, drum wear is beyond acceptable level. Does the brake drum require refinishing? If so, go to the next step. If not, go to step  14.
  13. Replace brake drum. See REAR BRAKE DRUM . After replacing brake drum, go to next step.
  14. Inspect brake shoes for proper adjustment. See REAR DRUM BRAKE SHOES  under ADJUSTMENTS. Are brake shoes adjusted properly? If so, go to step  18. If not, go to next step.
  15. Inspect brake drum components and brake drum adjustment hardware system for free movement and correct operation. Do drum brake adjusting hardware components operate freely and correctly? If so, go to step  17. If not, go to next step.
  16. Replace drum brake adjusting hardware components as necessary. See DRUM BRAKE ADJUSTMENT HARDWARE  under REMOVAL & INSTALLATION. After completing replacement, go to next step.
  17. Adjust drum brake shoes. See REAR DRUM BRAKE SHOES  under ADJUSTMENTS. Were you able to complete the adjustment? If so, go to step  20. If not, return to symptom table.
  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, go to step  20.
  19. Repair or replace drum brake backing plate as necessary. See BRAKE BACKING PLATE  under REMOVAL & INSTALLATION. After completing repair, go to next step.
  20. Install or connect components that were removed or disconnected during diagnosis.
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