Combination (Proportioning) Valve

If premature rear wheel skid occurs on hard brake application, it could be an indication that a malfunction has occurred with the proportioning valve portion of the combination valve.
To test the proportioning valve when the rear wheels of the vehicle slide first, leave the front brakes tubes connected to the combination valve, and proceed to test the proportioning valve for the rear brakes as follows:






1. Remove the brake tube coming from the master cylinder at the combination valve.
2. Remove the brake tube going to the rear wheels from the combination valve .

CAUTION: Pressure Test Fittings, Special Tool 8187, has two different size thread tube fittings. Be sure pressure test fitting being installed in combination valve has the correct thread size for installation in the combination valve and the installation of the brake tube fitting.

3. Install correct Pressure Test Fitting, Special Tool 8187, into the port of the combination from which the master cylinder brake tube was removed from.
4. Install correct Pressure Test Fitting, Special Tool 8187, into the port of the combination from which the rear wheel brake tube was removed from.






5. Install pressure gauge, Special Tool C-4007-A, into each of the Pressure Test Fittings, Special Tool 8187.
6. Have a helper exert pressure on the brake pedal (holding pressure) to get a reading on the valve inlet gauge and check the reading on the outlet gauge. If the inlet and outlet pressures do not agree with the values on the following chart, replace the valve.





PROPORTIONING VALVE PRESSURE SPECIFICATIONS