Description And Operation
The hydraulic brake system uses the principles of fluid power to apply the front and rear brakes. The hydraulic brake system operates as follows:
- The brake pedal is connected to a hydraulic servo called the master cylinder.
- When the pedal is pushed, a solid column of fluid is pushed from the master cylinder through metal tubing and flexible hoses to the rear brake wheel cylinders and front disc brake calipers.
- The wheel cylinders and calipers are hydraulic actuators where the hydraulic pressure produced in the master cylinder is converted into motion.
- The pistons in the rear wheel cylinders are forced outward against brake shoes which contact a metal braking surface on the brake drum.
- The front brake caliper pistons move inward against the brake pads and contact the metal braking surface of the brake rotor.
- When the brake pedal is released, the pressure in the system is relieved and the brake shoes and pistons return to their neutral or unapplied position.
The brake lines are arranged to form a split diagonal hydraulic system. Although the physical layout of the brake lines 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 remaining circuit supplies pressure to the right front and left rear. The hydraulic system is split in this manner as a safety precaution. If hydraulic pressure is lost in one circuit, the remaining circuit can provide less efficient but balanced braking.
If brake fluid is lost from one or both circuits, a low fluid level sensor in the master cylinder will illuminate an indicator lamp in the instrument cluster. The lamp comes on when a float in the master cylinder drops below a specified level and completes the circuit. Once the circuit is closed, the lamp will come on and remain on whenever the ignition switch is in the ON or START position. If the lamp is ON, make sure the parking brake is in the fully released position. The same lamp indicates when the brake fluid level is low and when the parking brake has been applied.
A proportioning valve is installed in the system to balance front to rear brake application. The valve reduces hydraulic pressure to the rear brake wheel cylinders to prevent rear wheel lock-up. Internally, the valve contains plungers that are shifted by hydraulic pressure to limit the output pressure to the rear wheels.