Brake Master Cylinder: Testing and Inspection

GENERAL CHECK
These checks will not determine all master cylinder malfunctions. Refer to the brake diagnosis to help isolate a problem if it is not found here.
1. Check for a cracked master cylinder casting, or brake fluid around the master cylinder. Leaks are indicated only if there is at least a drop of fluid. A damp condition is not abnormal.
2. Check for binding pedal linkage and incorrect pushrod length. If both are okay, remove the master cylinder reservoir cap and check for a swollen or distorted diaphragm. If a swollen diaphragm is found, substandard or contaminated brake fluid should be suspected.

ON-VEHICLE SERVICE
The master cylinder for this antilock brake system is to be serviced only by replacement. Do not attempt to repair or overhaul it. The fluid level sensor is part of the reservoir and cannot be replaced without replacing the reservoir. Lubricate rubber parts with clean brake fluid to ease assembly. Do not use lubricated compressed air on brake parts, as damage to rubber components may result. If any hydraulic component is removed or disconnected, it may be necessary to bleed all or part of the brake system. The torque values specified are for dry, unlubricated fasteners. Perform service operations on a clean bench, free from all mineral oil deposits.