Brake Fluid: Description and Operation

Brake Fluid

Brake fluid is hygroscopic, i.e. it has the tendency to absorb water and moisture from the air.

If water has been absorbed, the boiling point will drop, i.e., during high braking temperatures the brake fluid may develop steam bubbles and cause the brakes to fail.





Over time, brake fluid will darken in color. Dark colored brake fluid does not specify anything about its quality. The coloring occurs through chemical reactions and can occur after a short time (several weeks), especially in vehicles with Antilock Brake System (ABS).

CAUTION!
Avoid any contact of rubber components of the brake system (boots, seals) with mineral oil, gasoline and/or cleaning solvents!

Even the smallest amount of mineral oil, gasoline or solvents on a seal or boot can cause the part to change and thereby affect the function of the brake system. The results of an unclean brake system first show themselves months later, causing increased repair costs, especially on vehicles with ABS.

A = boot - original size





B = boot - swollen due to contact with mineral oil

The above mentioned points require special rules for handling:

Always keep brake fluid containers properly sealed. This is the only way of preventing contamination by oil, dirt, cleaning agents or moisture.

Brake fluid containers should be kept completely separate from oils (including hydraulic fluid) and cleaning agents to prevent any mixture of fluids or even filling of the brake system with an incorrect fluid.