Brake System

Applying the brake pedal uses lever action to push a rod into the brake booster, which through the use of vacuum or hydraulic pressure, boosts the force of the rod and then transmits this force to the primary piston in the master cylinder. This produces hydraulic pressure in the master cylinder. This pressure builds in the master cylinder and brake tubes as the brake pedal is depressed further. The pressure between the primary and secondary piston forces the secondary piston to compress building pressure in its circuit. The hydraulic pressure is transmitted by brake fluid through the brake tubes to the ABS Hydraulic Control Unit (HCU), which then distributes that pressure to the individual brake calipers. The brake calipers use hydraulic pressure to apply the pads. The application of the brake pads will cause the rotation of the wheels to slow or stop, depending on how much brake pressure is applied. The parking brakes carry out the same function except that they are mechanically actuated by a cable that connects only to the rear brakes.

Depending on application, some vehicles will be equipped with a Hydro-Boost® brake booster and some will be equipped with a standard vacuum brake booster. The Hydro-Boost® system uses the power steering system to boost brake pedal pressure while the vacuum system uses engine manifold vacuum or a brake vacuum pump (diesel engines) to boost brake pedal pressure. For a complete description on the operation of both systems, refer to POWER BRAKE ACTUATION .