Hydraulic System: Description and Operation
DESCRIPTIONThe hydraulic brake system includes the following components:
- Brake master cylinder
- Brake load sensor proportioning valve
- Brake hydraulic tubes
- Front brake hoses
- Front disc brake calipers
- Rear wheel cylinders
OPERATION
The hydraulic brake system uses the principles of hydraulic power to apply the front and rear brakes. The brake pedal is connected to the brake master cylinder. When the brake pedal is pushed, a solid column of fluid is pushed from the brake master cylinder to the front disc brake calipers and the rear wheel cylinders.
The front disc brake calipers and rear wheel cylinders are hydraulic actuators in which the hydraulic pressure produced in the brake master cylinder is converted into motion. The front disc brake caliper pistons move out, forcing the brake pads and linings to contact the front disc brake rotors. The rear wheel cylinder pistons move out, forcing the rear brake shoes and linings to contact the brake drums.
When the brake pedal is released, the pressure in the system is relieved. The front disc brake caliper pistons move in and the rear wheel cylinder pistons move in. The brake shoes and linings return to their unapplied position.
The inboard front brake pads and linings have wear indicators. When the front brake pads and linings are worn, the indicator contacts the front disc brake rotor and makes a squealing noise. The noise is a warning that the brakes need service before any damage occurs to the front disc brake rotor.
Double-walled steel brake tubing extends from the brake master cylinder pressure fittings out toward the wheels. Brake hoses make the final connection between the body-mounted brake tubes and the front disc brake calipers and the rear wheel cylinders.
The brake tubes are arranged to form a split diagonal hydraulic system. Although the physical layout of the brake tubes do not indicate it they are arranged to form an "X." One side of the 'X" supplies hydraulic pressure to the left front and right rear. The other side supplies pressure to the right front and left rear. The hydraulic system is split this way as a safety precaution. If hydraulic pressure is lost in one circuit, the remaining circuit can provide less efficient but balanced braking between the front and rear brakes.
If brake fluid is lost from one or both circuits, a brake master cylinder fluid level sensor in the brake master cylinder reservoir will illuminate the red brake system warning indicator in the instrument cluster. The indicator illuminates when the float in the brake master cylinder reservoir drops to a predetermined level and completes the circuit. Once the circuit is closed, the indicator will come on and stay on whenever the ignition switch is in the ON or START position. The same brake warning indicator also illuminates when the parking brake is applied.