Brake Master Cylinder Replacement
What is a brake master cylinder?
The master cylinder is mounted under the hood, in front of the brake pedal. It is the first step to developing braking force, and simultaneously controls the action of the individual brakes.
How does the brake master cylinder work?
When the brake pedal is pressed, the master cylinder pushes fluid under high pressure to the brake calipers, forcing them to squeeze the brake pads into the brake rotor. This pressure is created by two small plungers inside the master cylinder that compress the brake fluid as the brake pedal pushes them forward.
A failing brake master cylinder can cause the brake pedal to sink, feel spongy, and be unresponsive when depressed. It may also feel like the brake pedal goes all the way to the floor when braking. This is a very serious condition—the car should not be driven.
A defective brake master cylinder can set a diagnostic trouble code and cause a warning light on the dashboard to illuminate.
Brake master cylinders are often replaced when they begin to leak brake fluid.
What are the symptoms related to a bad brake master cylinder?
The term 'spongy' is well known in the automotive field, and describes the feeling of the brake pedal when air has been introduced into the master cylinder, or the master cylinder has pushed air into the brake lines. The brake pedal may also sink to the floor when pressed and held. This indicates the plungers inside the master cylinder are leaking internally, and will not produce the pressure needed to cause the vehicle to slow or stop.
Learn more about brake master cylinder symptoms