Master Cylinder Diagnosis

The following inspections will help locate master cylinder malfunctions. Use the Brake Diagnosis Charts in Brake System Diagnosis in order to help isolate the problem if the problem is not found through the following tests:
1. Inspect for a cracked master cylinder casting.
2. Inspect for brake fluid around the master cylinder. A leak exists 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 and check 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 is contaminated, use the following procedure:

Disassemble and clean the serviceable components.
^ Replace all of the non-serviceable components.
^ Flush all of the pipes and the brake hoses.

Antilock Brake System Refer to brake modulator (ABS)/Master Cylinder Assembly Replacement in Antilock Brake System.