Brake Fluid General Information

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Brake Fluid Is Hygroscopic, Meaning That It Has the Ability to Absorb Water and Moisture from the Air.

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

Fig 1: Brake Fluid Graph

Courtesy of AUDI OF AMERICA, LLC

Over time, brake fluid will darken in color. Dark-colored brake fluid does not specify anything about its quality. The color forms due to chemical reactions.

Even the smallest amount 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.

Fig 2: Boot Original Size -A- And Swollen From Contact With Mineral Oil -B-

Courtesy of AUDI OF AMERICA, LLC

A -

Boot - Original Size

B -

Boot - swollen through contact with mineral oil

As a Result of the Previously Mentioned Points:

Keep containers of brake fluid closed securely. This is to make sure that no oil, dirt or cleaning materials and no humidity can enter the container.
Store containers of brake fluid away from oil (even hydraulic oil) and cleaning fluids to prevent an accidental mixing of both fluids or even filling the brake system with the wrong fluid.

WARNING:

Health Risk.

Brake fluid is poisonous. NEVER siphon brake fluid by mouth!
To prevent skin contact with brake fluid, wear chemical resistant safety gloves.
Follow all disposal regulations.

Risk of accident due to steam bubbles developing when the water content in the brake fluid is too high.

Brake fluid is hygroscopic, meaning that it absorbs moisture from the surrounding air.
Seal the open brake hoses and brake line with plugs from the Assembly Part Set: 5Q0 698 311 .
Always store brake fluid in air-tight containers.

Malfunctions from contact with brake fluid with fluids containing mineral oils.

Brake fluid must never come into contact with fluids containing mineral oils (oil, gas, cleaning solutions). Safety gloves must be free of oil and grease.

Risk of damaging the painted surfaces.

Due to its caustic nature, brake fluid must also never be brought into contact with paint. Wash off any spilled brake fluid immediately with plenty of water.

NOTE:

Only use new brake fluid.