Brake Fluid: Not One of Your Car’s Most Famous Fluids, but still…

“Check your oil level!” “Don’t let that transmission fluid get too low!!” These and other fluid-isms are no doubt familiar to you as you go about the business of maintaining your vehicle. Heck, even your windshield washer fluid probably gets higher billing than that most anonymous of fluids…the Brake Fluid.

When you think brakes, you think rotors, pads (and screeching, of course). But proper brake care depends heavily on attention paid to your fluid. See below for a brief overview of how brake fluid works and a summary of what’s involved in maintaining the stuff.

Word of the Day: Hygroscopic

Hygroscope means something attracts and retains moisture. In many life situations, moisture can be good, of course, but for your braking system, not so much. The accumulation of moisture can decrease brake performance and lead to corrosion of components. In addition, a greater moisture component can also lower the ‘boiling point’ of the brake fluid. If that doesn’t sound good, it’s not. Fresh brake fluid (containing no water/moisture) is virtually incompressible. That means when you press the brake pedal, the fluid acts almost like a solid ‘bar’ of material, transferring the pressure you apply to the pedal, to cylinders, that in turn clamp down on your brake pads, thereby stopping your wheels.

When the brake system heats up – as with repeated and, particularly, frequent braking on the same trip – the brake fluid can eventually ‘boil’, meaning some of the fluid begins to transform into a gaseous state. This leaves bubbles in the brake fluid. As you can imagine, bubbles are not incompressible. They can easily be ‘squished’, or compressed. That means for a given force you apply to the brake pedal, part of that force is used up compressing the bubble-filled fluid. The end result? You find yourself needing to press harder on the brake pedal to get the same effect.

Brake Fluid Care

There’s a simple solution to all of this, and that is to change the brake fluid regularly! By refreshing your system with new brake fluid you give yourself a new ‘incompressible’ system that provides for optimal braking performance. Of course, this can be easier said than done, as brake fluid is considered by some experts to be the single most neglected component in automobile maintenance.

A complete brake flush is recommended at least once every two years. Keep in mind that a complete flush is different than a smaller ‘bleed’ of the system, in which an amount of brake fluid is removed from the system during work on a component/s of the system; a small amount of new fluid is then added to return the fluid level to normal. Rather, we recommended a periodic full flush of the brake system.