Component Tests and General Diagnostics

Improper brake fluid, mineral oil (i.e., power steering fluid and transmission fluid) or water in the fluid may cause the fluid to boil, or the rubber components in the brake hydraulic system to deteriorate. If the master cylinder cap diaphragm is swollen, then rubber parts have deteriorated. This deterioration may also be evidenced by swollen wheel cylinder boots and caliper boots.

If deterioration of rubber parts is evident, disassemble all serviceable hydraulic components, and wash with alcohol. Dry the parts with non-lubricated compressed air before assembly to keep alcohol out of the system. Replace ALL rubber parts in the system, including hoses and non-serviceable hydraulic components. After reassembly, fill the system with new brake fluid, flush and bleed it. Also, flush the system if you have any doubt as to the grade of fluid in the system, or if fluid has been used that has been in contact with parts/components which have been subjected to contaminated fluid. When working on calipers, check for fluid on linings. If excessive fluid is seen, replace the linings.