REMOVAL & INSTALLATION
See Figure 1
LH platform vehicles not equipped with Antilock Brakes, have a proportioning hydraulic system control valve in the brake hydraulic system. The valve is attached to the frame rail below the master cylinder. The proportioning valve balances front to rear braking by controlling at a given ratio, the increase in rear system hydraulic pressure above a preset level. Under light pedal application, the valve allows full hydraulic pressure to the rear brakes.
There is only one valve assembly in each vehicle which is not equipped with Antilock Brakes. During any service procedures, identify the valve assembly by part number.
The hydraulic brake system on non-ABS vehicles is split diagonally. The left front and right rear brake are part of one system. The right front and left rear are part of another. When removing and installing a proportioning valve, correct brake line identification and placement is most important. Both systems are routed through but are hydraulically separated by the proportioning valve. Since the brake systems are split diagonally, the vehicle will retain 50% of its stopping capability in the event of a failure in either half. To remove the proportioning valve, use the following procedure.
- Disconnect the negative battery cable.
The proportioning valve is located below the master cylinder mounted to the frame rail.
- Tag and disconnect the brake lines from the valve. Be sure to plug the brake lines so that the hydraulic system does not become contaminated with dirt or moisture.
- Remove the proportioning valve from the engine compartment.
- Verify correct replacement part number, if installing replacement valve. Install the proportioning valve to the frame rail. Tighten the mounting bolts.
- Reconnect the brake lines to the valve. Be sure that the fittings are connected to their correct valve openings. Tighten the brake line fittings to 13 ft. lbs. (17 Nm).
- Add brake fluid reservoir to the MAX level, using DOT 3 type brake fluid only. Bleed the brake system.
- Test drive the vehicle, with caution, to ensure proper brake operation.