Brake Fluid: Testing and Inspection

COLOR - Hydraulic brake fluid color must conform with the requirements of Federal Motor Vehicle Safety Standard 116. Under this standard, brake fluids are visually different from other automotive fluids such as transmission, power steering and engine oil.

DISCOLORATION - The color of the fluid in a normal brake system in service can vary from its original color for many reasons. Sometimes a brake master cylinder may show significantly different shades of color of fluid between the two brake master cylinder reservoir compartments. Color may appear to vary between cast steel and die cast aluminum reservoirs. Some of the reasons for the apparent difference or discoloration in a system are listed below:
^ Fluid discoloration can occur due to heat and/or aging.
^ Difference in fluid color of a two-compartment brake master cylinder reservoir can be due to the different operating temperatures or different rates of normal oxidation between the two reservoir compartments.
^ Fluid discoloration can exist when different brands/shades of brake fluid are used in topping off during normal service.
^ Fluid discoloration can occur through dissolution of color dye used on brake master cylinder internal springs in manufacturer's assembly procedure.

CONTAMINATION
NOTE: Brake fluid contaminated with a hydrocarbon / mineral based fluid (power steering or transmission fluid) can be detected by an obvious swelling of the master cylinder cap gasket.

WARNING: If the swollen brake master cylinder gasket condition is present, all brake system rubber parts must be replaced. All components containing rubber parts must be overhauled or replaced. All brake tubes must be thoroughly flushed with brake fluid before the vehicle goes back into service. Contaminated and swollen parts can lead to brake failure.

Contamination can be tested for by checking for obvious swelling of the master cylinder cap gasket. A second method for testing for contamination is to put a sample of the fluid into a jar of water. The brake fluid which is water soluble, will dissolve and turn the water white. The oil will float on top of the water as a film. If contamination is found all brake components with rubber components will need to be over hauled or replace and the system thoroughly flushed with new bake fluid.