Brake Fluid Yeah, it’s exciting…

Brake Fluid Specially blended hydraulic fluid that transfers pressure to the wheel brake assemblies Rated by the SAE and DOT SAE (Society of Automotive Engineers) DOT (Department of Transportation)

Fluid Types DOT 3 – 401/284 F DOT 4 – 446/311 F DOT 5 – 500/356 F DOT 3, 4, 5.1 basically the same DOT 5 is silicone based and not compatible

Fluid cont. Most passenger vehicles use DOT 3 or DOT 4 – look on reservoir cap Some performance cars use DOT 5, 5.1, or may have special spec Don’t mix fluid types

Which are the most common? DOT 1 and 2 DOT 2 and 3 DOT 3 and 4 DOT 4 and 5 DOT 5 and 6 DOT 5.1 and 5.2

Brake Fluid Brake fluid must have the following characteristics: correct viscosity at all temperatures high boiling point noncorrosive water tolerant lubricates components low freezing point

Viscosity means: How a fluid reacts under pressure A fluids compressibility factor The fluids resistance to flow It’s boiling temperature It’s freezing point None of the above

Brake Fluid (cont) Miscibility – the ability to mix with similar fluids Hygroscopic – the ability of a substance to attract water (moisture) from the surrounding environment

Brake fluid absorbs moisture from the air at the rate of about 2% per year. As the brake fluid absorbs water, its boiling temperature decreases.

Brake fluid should be replaced: Once a year At every oil change Twice a year Every other year In March With power steering fluid Brake fluid should not be replaced

Brake Fluid Precautions Keep off painted surfaces, wiring, and plastics Keep container closed Do not reuse old fluid Do not mix DOT 3 or 4 with DOT 5 Wear proper gloves when handling Wash immediately if it gets on skin

Brake Fluid and Paint

Why keep brake fluid in a closed container? It likes the dark It absorbs moisture It will evaporate It has viscosity None of the above