553 Brake Systems Technician Handbook Master Cylinder The master cylinder converts the motion of the brake pedal into hydraulic pressure. A tandem master cylinder consists of: • Reservoir tank • Piston(s) • Cylinder Most vehicles use a tandem master cylinder, where the cylinder is separated into two chambers: • The primary chamber at the rear of the master cylinder feeds the rear wheels. • The secondary chamber at the front of the master cylinder feeds the front wheels. Dividing the cylinder into two chambers provides a safety factor. If one circuit looses pressure, the other remains functional. The reservoir tank stores brake fluid.
A separator in the reservoir ensures sufficient fluid for at least one circuit (in case of a leak in the other circuit). The cap contains a small vent hole that allows the fluid to expand and contract. A diaphragm separates the fluid from contact with the air. 10 Technical Training