GM Service Manual Online
For 1990-2009 cars only

The following conditions indicate substandard or contaminated fluid:

    • Swollen master cylinder cap diaphragm
    • Swollen wheel cylinder boots
    • Swollen caliper piston boots

Use the following tests in order to locate some master cylinder malfunctions.

  1. Inspect for a cracked master cylinder casting.
  2. Inspect for brake fluid around the master cylinder. A leak is present if there is at least one drop of fluid. A damp condition is not abnormal.
  3. Inspect for binding pedal linkage.
  4. If the pedal linkage and the pushrod length are correct, remove the master cylinder reservoir cap. Inspect for a distorted or swollen diaphragm.
  5. If a swollen diaphragm is found, substandard or contaminated brake fluid is the probable cause. If the fluid if contaminated, use the following procedure:
  6. 5.1. Disassemble and clean the serviceable components.
    5.2. Replace all of the rubber and non-serviceable components.
    5.3. Flush all of the brake pipes and brake hoses. Refer to Hydraulic Brake System Flushing .