Q: What causes brake fluid leaks?

There are many factors that can lead to brake fluid leaks.

Let’s begin at the start of the system, with the master cylinder. This is a sealed unit with a reservoir to hold the brake fluid needed to operate the system. It may include a sensor that will illuminate a light to indicate a low level. The actual operational part of the master cylinder contains internal pistons with seals to build the pressure needed to squeeze the brake pads or shoes to stop your car. The brake booster rod pushes on these pistons, which have an external rear seal to keep the fluid trapped inside the cylinder. When the brake pedal is depressed, the pistons push the fluid and transfer the pressure through the brake system. Over time these seals can become worn and leak either internally or externally. A sign of an external leak is an area of missing or peeling paint on the brake booster just below the rear of the master cylinder. If the brake pad wear is excessive, it is possible for the caliper pistons to be overextended in their bores and pop out past the seal, causing fluid to leak past the piston. Flexible rubber brake lines can dry, rot, and crack or be damaged from abuse, road debris, or an accident. Metal brake lines can rust out, especially those subject to severe conditions where excessive salt is used in winter weather conditions. If the vehicle is near a salt water source, it can have the same effect on the lines over time. The seals in wheel cylinders will also wear over time and can leak fluid out onto the brake shoes. Even a loose brake bleeder screw can cause a leak.

Have your vehicle checked if you notice problems like a low brake pedal or a pedal that sinks down as you sit at a light with pressure applied to the brake pedal. No problem with your vehicle should be ignored, but certainly anything to do with the brakes, tires, steering, or fuel system leaks should be addressed as soon as you feel them occur. As with all concerns, regular maintenance checks will help to keep potential problems in check.