Brake Master Cylinder: Testing and Inspection

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. If the problem is not found through these tests, refer to Brake System Diagnosis in order to isolate the problem. Symptom Related Diagnostic Procedures
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:
- Disassemble and clean the serviceable components.
- Replace all of the rubber and non-serviceable components.
- Flush all of the brake pipes and brake hoses. Refer to "Hydraulic Brake System Flushing".