Proportioning Valve

The test procedure is the same for either rear proportioning valve. After road testing the vehicle to determine which wheel skids first, follow the procedure for testing the suspect proportioning valve. See Fig 1.

1. Using a brake pedal holding tool, depress the brake pedal past its first 1" of travel and hold it in this position. This will isolate the master cylinder from the brake hydraulic system and will not allow the brake fluid to drain out of the master cylinder reservoir.
2. Determine which proportioning valve needs to be tested.
3. Remove the hydraulic brake tube from the proportioning valve controlling the rear wheel of the vehicle that has premature wheel skid.
4. Remove the proportioning valve from its outlet port on the master cylinder.
CAUTION: Be sure the pressure test fittings being installed into master cylinder and proportioning valve, have the correct thread sizes needed.
5. Install the Brake Pressure Adapters, Special Tool (8644 and 6805-3) onto the proportioning valve.
6. Install the proportioning valve (with tools) back into the outlet port on the master cylinder.
7. Attach a Pressure Gauge, Special Tool (C-4007-A), to each pressure adapter.
8. Remove the brake pedal holding tool. Bleed any air out of the pressure gauge hoses at the pressure gauge.
9. With the aid of a helper, apply pressure to the brake pedal until the reading on proportioning valve inlet gauge is at the target inlet pressure. See BRAKE PROPORTIONING VALVE APPLICATIONS & PRESSURE SPECIFICATIONS  table. If the inlet gauge pressure overshoots its target pressure when the pedal is depressed, release the brake pedal, relieving the pressure in the system, before reapplying the pedal to reach the target pressure at the inlet gauge. This is necessary to get an accurate reading of the outlet pressure.
10. Once inlet pressure has been achieved, check the pressure reading on the proportioning valve outlet gauge. If the proportioning valve is within pressure specifications, the valve is good and does not require replacement.
11. Reinstall the brake holding tool on the brake pedal and remove the test equipment from the vehicle.
12. Remove the tools from the proportioning valve.
13. Install the proportioning valve in the master cylinder and hand tighten until the proportioning valve is fully installed and its O-ring seal is seated into the master cylinder. Tighten the tube nut to 13 ft. lbs. (17 N.m). Bleed the affected brake line. See BLEEDING BRAKE SYSTEM .

Fig 1: Locating Proportioning Valve

Courtesy of CHRYSLER CORP.