1. Brake Fluid
Yeah, it’s exciting…

2. 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)

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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.

10. 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

11. 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

12. Brake Fluid and Paint

13. 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