Brake Fluid: Testing and Inspection

DIAGNOSIS AND TESTING - BRAKE FLUID CONTAMINATION
Indications of fluid contamination are swollen or deteriorated rubber parts. Swollen rubber parts indicate the presence of petroleum in the brake fluid.
To test for contamination, put a small amount of drained brake fluid in clear glass jar. If fluid separates into layers, there is mineral oil or other fluid contamination of the brake fluid.
If brake fluid is contaminated, drain and thoroughly flush system. Replace master cylinder, proportioning valve, caliper seals, wheel cylinder seals, Antilock Brakes hydraulic unit and all hydraulic fluid hoses.