We change our transmission fluid every 25,000 or 50,000 miles, or at least we should.
We change our brake fluid. Wait a minute do we change our brake fluid? The answer for most people is we never change our brake fluid. Why should we our brake fluid, the brakes still work. Why do we change motor oil and transmission fluid, because expert tell us to. According to the experts brake flluid should be every 12 to 24 months as preventive maintenamce, even more in wet and extremely humid climates.
What does water have to with brake fluid? Brake fluid absorbs water from contact with air.
Once a bottle is open it starts absorbing water.
Brake Fluid Failure
There are two basic failure modes for brake fluid: It can boil, and it can cease to provide adequatelubrication and corrosion protection. Both are the results of contamination. usually with water or petroleum products. DOT 3and DOT 4 glycol brake fluid are hygroscopic, they absorb water easly and hold it in suspension, much like antifreeze. The second the cap is removed from the bottle brake fuild, thebrake fluid begins absorbing water from the air. And while brake fluid is kept in a slosed system, moisture seeps into the brake system continuously through the various seals and microscopic pores onf the flexible brake lines. Moisture absorption through the brake system accelerates as vehicles age, aand there's almost no limit to how much water brake fluid can absorb. Water lowers the boiling point of brake fluid, which will evenually lead to fairlure. After two years of serivce, the average boiling point of brake fluid will have dropped below the minimum federaul requirement.
High Boiling Points Prevent Failure
As the brake system heats up, brake fluid with low boiling point begins to vaporize. The brake pedal must travel further to apply the same amount of force on the brakes, causing a spongy feeling. If enough of the brake fluidis vaporized, brake system failure may occur.
Brake fluid boiling points are meassured on two separete scales:
- Dry equilibrium reflux boiling point (ERBP) - the boilong point of new, frreshly opened unused fluid
- Wet ERBP- the boiling point of a brake fluid after it has absorbed three percent water.
The Department of Transportation (DOT) has set minimum requirement to ensure brake fluids will provide adequate protection. The minimum dry ERBP for DOT brake fluid is no less than 205 C(401 F), the minimum wet ERBP is 140C (284 F) it only takes four persent water to contamination to bring dot 3 fluid's boilng point down to the federal limit.
AMSOIL Brake fluid exceeds government stadards. They feature high wet boiling points for maximum life, supeerior performace and reliable braking, even in extreme condidtions.
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