Brake Fluid 101 – What Is It? Why Do I Need It? Repair

What Role Does Brake Fluid Play When You Brake?

When you press on your brake pedal, the connected master cylinder containing brake fluid simultaneously compresses a piston in the brake caliper at each wheel. In this way, the brake fluid is part of what creates the force that clamps your brake pads around your rotors, ultimately slowing your car’s motion.

Contamination Moisture Can Wreak Havoc

Because brake fluid is hygroscopic, it absorbs moisture from the air. This can’t be prevented but over time it will degrade your brake fluid and lower the boiling point. Brake fluid has a very high boiling point because so much heat is generated during the operation of your brakes. A lower boiling point would cause a lot of damage to the parts in your brake system. Water has a much lower boiling point than brake fluid, so the more contaminated your brake fluid is with moisture from outside the system, the more likely damage is to your brake system.

The Air In Your Brake Fluid Will Make It Less Effective

Similarly, if you get air in your brake fluid, you’ll notice a spongy or soft brake pedal that’s less effective at slowing your car. This is because the air keeps your car’s brake fluid from flowing properly, which makes the moving parts triggered by the brake fluid’s motions more delayed or less effective. If you notice a spongy brake pedal, bleeding the brakes can eliminate the air pockets from your brake fluid and increase effectiveness when braking.

The Higher the DOT Rating, the Longer it Should Last

Your brake fluid’s DOT (Department of Transportation) rating corresponds to its boiling point, both wet and dry. DOT sets safety regulations to ensure all brake fluid will perform at a certain level but generally speaking, the higher the boiling point, the longer the lifespan of the brake fluid. So if you’re looking at brake fluid to top off your car or your mechanic tells you what they used, look for a higher DOT rating.