The ability of the Plymouth brake master cylinder to take mechanical motion and change it into hydraulic pressure is how this safety system is made to function. It all begins when the driver of the Plymouth applies pressure to the brake pedal. It is this action of pressure on the brake pedal that moves the piston in the brake master cylinder. This movement forces a buildup of pressure in the brake lines and hoses so the pistons in the wheel cylinders and calipers can be forced outward, causing friction where the pads and shoes press against the rotors and drums. The only failure of the Plymouth brake master cylinder is the seals on the piston it contains inside of it. When these polymer seals rupture, the pressure cannot be built up in the braking system. Unlike other polymer seals that rupture in your Plymouth braking system, the ones located in the brake master cylinder will not cause a brake fluid puddle to form under your vehicle. This is how a driver will know the master cylinder is malfunctioning because there is no external indication of a problem like when a caliper or line is leaking. There is also no air entering into the system, just the lack of ability to build up pressure. The replacing of the brake master cylinder is done by removing the brake lines and the two mounting bolts that attach it to the vacuum drum on the firewall of your vehicle. The most difficult part of this procedure of replacing the brake master cylinder is the bleeding of air from the brake system. Once that is completed, the Plymouth will be ready and safe to be driven on the road again.