As cars become more reliable and last longer, we are hearing more and more about the importance of maintaining fluids and preventative maintenance. Brake fluid is a vital fluid in your vehicle and should be serviced on a regular basis to maintain your braking performance and prevent expensive brake components from failing prematurely. What people don’t usually understand is why brake fluid needs to be flushed.
Brake fluid transfers the energy of your brake pedal to the brake calipers, squeezing the brake pads together against the brake rotor creating friction and heat and stopping the vehicle. During this process fluid is subjected to extremely high temperatures, usually over 300 degrees as the brakes heat up and the vehicle stops. Brake fluid must endure very high temperatures and not turn into vapor (boil).
Another key property that makes brake fluid unique is that brake fluid is hygroscopic meaning it absorbs water. If moisture was allowed to settle in the system it would rust out the metal components. The problem with brake fluid absorbing moisture is that it lowers the boiling point the more it absorbs. You will see brake fluid rated in two ways, “DRY” and “WET” boiling points, because of the changing boiling points as moisture is absorbed.
As you can see, the more moisture in the system the lower brake fluid boils. When the temperature of the brake system exceeds the boiling point of the fluid, the system will loose pressure and you get “Brake Fade” or what people describe as a “Spongy Brake Pedal”. Usually this happens when making a panic stop or when the vehicle is loaded down with passengers, thus making brake failure even more problematic. For this reason, it is important to always have fresh fluid in the system to keep the boiling point above the normal operating temperature of the brake system and to prevent brake failure.
As if boiling fluid wasn’t enough reason to flush your brake fluid, old fluid causes many expensive failures such as leaking brake calipers, a leaking master cylinder, a damaged ABS pump, or failing brake lines.
When looking at fluid or when your mechanic is reporting the condition, dark brown brake fluid indicates high moisture content. Green brake fluid indicated the old fluid is leeching copper from the system due to the pH being off. Both are problematic to the vehicle and the safety of the occupants and the very expensive parts in the brake system.
A Brake Fluid Flush replaces the old fluid in the reservoir with a new bottle (never being exposed to moisture in the air) of fresh fluid and then flushed the new fluid through the brake lines and through all 4 calipers. Typically this should be done every 2 years but it varies a bit depending on the vehicle. The result is a longer lasting brake system, shorter and more consistent stopping distances, and a happier vehicle with a lot less money spent on repairs!