Proportioning Valve Testing

Fig 3 Testing Proportioning Section Of Combination Valve:

Symptom
Premature rear wheel slide on brake application could be an indication that the fluid pressure to the rear brakes is above the reduction ratio for the rear line pressure and that a malfunction has occurred in the proportioning valve unit.
- If this symptom is experienced the proportioning valve should be tested.

NOTE: During testing, leave front brake lines connected to the valve.

Proportioning Valve Unit Test
1. Install one gauge and "T" of set C-4007A or equivalent, between brake line from master cylinder secondary port and brake valve assembly.
2. Install a second gauge to the rear brake outlet port between the valve assembly and the rear brake line.
- An adaptor tube, made up locally of a 9/16 x 18 tube nut, short piece of brake tube and 3/8 x 24 tube nut will be required to connect the hose to the valve.
3. Bleed the rear brake system.
4. Have a helper exert and hold pressure on the brake pedal 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.
5. Valve assemblies for all models are shipped in the front failed position to improve bleeding.
- When installing a new valve, bleed the rear brakes first.
- After bleeding both front and rear systems, applying the brakes with moderate force will hydraulically reset the switch and turn off the warning light.

Hold-off cut in pressure 117 PSI
Split Point (PSI)/Slope 300/0.27
ID tag color White