Without Antilock Brakes

If premature rear wheel skid occurs on a hard brake application, it could be an indication that a malfunction has occurred with one of the proportioning valves.

Non-ABS Proportioning Valve Location On Master Cylinder:

One proportioning valve controls the right rear brake, and the other proportioning valve controls the left rear brake. Therefore, a road test to determine which rear brake skids first is essential.

Before testing the proportioning valve in question, inspect the rear brake linings for contamination or for replacement shoes not meeting the OEM brake lining material specifications.

The proportioning valve should always be tested prior to being replaced.

The in-line proportioning valves used on this vehicle require special pressure fittings to test the proportioning valves for proper proportioning valve function. The pressure fittings are installed before and after the proportioning valve being tested to verify proportioning valve is maintaining the required hydraulic pressure to the rear wheel brake which it controls.

The testing of proportioning valves for this vehicle, if equipped with Antilock Brake System (ABS), can be found in the Antilock Brake System.

PROPORTIONING VALVE TEST (WITHOUT ABS)
The test procedure is the same for both rear proportioning valves. After road testing the vehicle to determine which wheel skids first, follow the procedure below for testing the suspect proportioning valve.

Brake Pedal Holding Tool:

1. Using a brake pedal holding tool as shown, depress the brake pedal past its first one inch 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. Use the figure shown to 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 of the master cylinder.

CAUTION: Be sure the pressure test fittings being installed into master cylinder and proportioning valve, have the correct thread sizes needed.

Proportioning Valve Installation For Pressure Testing:

5. Install the appropriate Pressure Test Fitting, Special Tool 6805-1 or 6805-2, into the outlet port of the master cylinder.
6. Install proportioning valve into the pressure test fitting installed in the master cylinder outlet port.
7. Install the appropriate Pressure Test Fitting, Special Tool 6805-3 or 6805-4, into the outlet port of the proportioning valve.
8. Install the brake hydraulic tube into the pressure test fitting that is installed in the proportioning valve being tested.

Brake Proportioning Valve Applications And Pressure Specifications:

Pressure Gauges Installed On Pressure Test Fittings:

9. Install a Pressure Gauge, Special Tool C-4007-A, into each pressure test fitting.
10. Remove the brake pedal holding tool. Bleed any air out of the hose from the pressure test fitting to the pressure gauge, at the pressure gauge.
11. With the aid of a helper, apply pressure to the brake pedal until the reading on proportioning valve inlet gauge is at the inlet pressure in the BRAKE PROPORTIONING VALVE APPLICATIONS AND PRESSURE SPECIFICATIONS table following this procedure. Once inlet pressure has been achieved, check the pressure reading on the proportioning valve outlet gauge. If the proportioning valve outlet pressure does not agree with value in the table, replace the proportioning valve. If proportioning valve is within pressure specifications, the valve is good and does not require replacement.
12. Reinstall the brake holding tool on the brake pedal and remove the test equipment from the vehicle.

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. Torque the proportioning valve to 40 Nm (30 ft. lbs.).
14. Install the brake tube on the proportioning valve. Torque the tube nut to 17 Nm (145 inch lbs.).
15. Bleed the affected brake line. See Brake Bleeding.