The brake master cylinder creates hydraulic pressure when the brake pedal is applied. This pressure is distributed to the brake pads or shoes which press against the brake drum or the brake rotor to slow down or stop the vehicle. A brake master cylinder replacement is needed when the master cylinder leaks either internally or externally and cannot create hydraulic pressure.
When performing a brake master cylinder replacement, the brake fluid must be removed from the brake fluid reservoir. Then the brake lines are removed from the old master cylinder and the new brake master cylinder is installed. Then brake fluid is added to the reservoir and a brake bleeder screw is opened at each wheel. Finally, the brake pedal is continually depressed until fresh brake fluid exits at all wheels.
Most manufacturers will cover the cost of a brake master cylinder replacement under the bumper to bumper warranty section of the factory warranty. There are extended auto warranties available that will cover replacing the master cylinder. The break master cylinder is usually covered under the more comprehensive coverage plans.