Q: How does brake fluid get dirty?

One way that brake fluid becomes contaminated is when moisture is absorbed by the brake fluid through rubber brake lines. This moisture will break down the brake fluid and cause rust in the brake system. Excess moisture in brake fluid will increase its temperature because the boiling point of water is lower than that of brake fluid. When this happens air gets into the brake lines and the brakes may become less effective. Brake fluid that has been contaminated by water or moisture can also weaken the master cylinder and caliper rubber seals and lead to brake leaks and an overall failure of the brake system. This type of contamination most commonly occurs in an environment that is particularly humid and in conditions of heavy braking. Another way that brake fluid becomes contaminated is when grime and debris from the brake system accumulates in the brake fluid. Over time, the heat that is generated from braking causes the brake fluid to break down and become contaminated. Brake fluid should normally be changed every two years but this is something that may already be included in the maintenance schedule for your vehicle. Pay close attention to the color of your brake fluid. Normal brake fluid should be a light yellow color and look almost clear, while contaminated brake fluid looks dark brown or black in color.