Proportioning Valve

DESCRIPTION






There are two fixed proportioning valves used in the antilock brake system. One valve controls each rear braking circuit, but both are serviced as one assembly. Both proportioning valves are mounted together on a bracket that is attached to the left frame rail near the left rear shock absorber.

The fixed proportioning valve is made out of aluminum and has an integral mounting bracket. The fixed proportioning valve assembly has 2 inlet ports for brake fluid coming from the ABS ICU, and 2 outlet ports for brake fluid going to the brakes at each rear wheel.

The fixed proportioning valve is a non-serviceable component and must be replaced as a complete assembly if found to be functioning improperly.

OPERATION
The fixed proportioning valve operates by allowing full hydraulic pressure to the rear brakes up to a set pressure point, called the valve's split point. Beyond this split point the proportioning valve reduces the amount of hydraulic pressure to the rear brakes according to a certain ratio.

Thus, on light brake pedal applications, the proportioning valve allows approximately equal brake hydraulic pressure to be supplied to both the front and rear brakes. On heavier brake pedal applications, the proportioning valve will control hydraulic pressure to the rear brakes, so that hydraulic pressure at the rear brakes will be lower than that at the front brakes. This controlled hydraulic pressure to the rear brakes prevents excessive rear wheel ABS cycling during moderate stops.