Symptoms of Brake Master Cylinder Failure

The ability to stop a car is obviously important, so keeping an eye on the condition of your brakes is important. So, what are the symptoms of a brake master cylinder failure?

The brakes in your car or truck work on the same system as an airplane – hydraulics. The system consists of the brake pedal which leads to a brake booster [most vehicles] and then to the brake master cylinder. The master cylinder then moves pistons to "squeeze" hydraulic liquid known by the highly technical name of brake fluid. This causes the liquid to push pistons or calipers at the wheels. When pushed, these activate the brakes at the wheel and the car slows. It is as simple as that.


So, what are the symptoms of a brake master cylinder failure? The first symptom is a warning light. Modern vehicles are models of ongoing diagnostic tests. The ECU is computer in charge of monitoring the brakes. This includes the master cylinder. If the cylinder fails, the sensors will note the decrease in hydraulic pressure in one of the lines going to one of the four wheels. When that occurs, you can expect the brake warning light to fire up on the dash.

What about older models? The answer is usually not a brake warning light. Instead, we have to go old school. The key symptom of master cylinder failure is not what you see or hear, it is what you feel. A master cylinder that is going bad is going to produce less pressure to the brakes. This will manifest in the brake pedal as a "mushy" or "soft" feeling. When you press down on the pedal, you might find the pedal slowly dropping to the floor or you might feel the need to press harder to get the stopping action you want.

The symptoms of a master cylinder need to be recognized and dealt with quickly. The good thing about a brake master cylinder failure is it happens in stages. The cylinder has separate lines going to each of the front and rear wheels. Both don't fail at the same time, but one can. When one fails or starts to, the other channel is put under tremendous pressure and that can lead to a full failure.

If you feel the mushy pedal symptoms of a brake master cylinder failure, do not procrastinate. Get it looked at before a small problem turns into a big one.

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