Without Antilock Brakes

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

Non-ABS Brakes 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 slides first is essential. Once the wheel which slides first is determined, use the following procedure to diagnose the proportioning valve.

The test procedure for a premature rear wheel skid is the same for both rear wheel proportioning valves. The pressure test fittings used for each proportioning valve though are different due to proportioning valve and brake tube nut thread sizes being unique for each rear wheel. After road testing vehicle to determine which wheel skids first, the proper test fittings required will have to be determined. Then follow the procedure below for testing the required proportioning valve.
1. After road testing vehicle to determine which rear wheel exhibits premature rear wheel skid, refer to to determine which proportioning valve needs to be tested.
2. Remove hydraulic brake tube from proportioning valve controlling the rear wheel of the vehicle which has premature wheel skid.
3. Remove proportioning valve from that outlet port of the master cylinder.

CAUTION: Be sure the pressure test fitting being installed into master cylinder, has the correct thread sizes for installation into the master cylinder and the installation of the proportioning valve.

Proportioning Valve Installation For Pressure Testing:

4. Install Pressure Test Fitting, Special Tool 6805-1 or 6805-2 or equivalents into the outlet port of the master cylinder, which the proportioning valve was removed from.
5. Install proportioning valve into pressure test fitting installed in master cylinder outlet port.

CAUTION: Be sure the pressure test fitting being installed into proportioning valve, has the correct thread sizes for installation into the proportioning valve and installation of brake tube fitting.

6. Install Pressure Test Fitting, Special Tool 6805-3 or 6805-4 or equivalents into the outlet port of the proportioning valve.
7. Connect brake hydraulic tube onto the pressure test fitting that was installed in proportioning valve.

Pressure Gauges Installed On Pressure Test Fittings:

8. Install a Pressure Gauge, Special Tool C-4007-A or equivalent into each pressure test fitting. Bleed air out of hose from pressure test fitting to pressure gauge, at pressure gauge to remove all trapped air. hose.

Brake Proportioning Valve Applications And Pressure Specifications:

9. With the aid of a helper, apply pressure to the brake pedal until reading on proportioning valve inlet gauge, is at the pressure shown on the following chart. Then check the pressure reading on the proportioning valve outlet gauge. If proportioning valve outlet pressure does not agree with value shown on the following chart, when inlet pressure shown on chart is obtained, replace the proportioning valve. If proportioning valve is within pressure specifications do not replace proportioning valve.
10. Check rear wheel brake shoe linings for contamination or for replacement brake shoes not meeting OEM brake lining material specifications. These conditions can also be a possible cause for a premature rear wheel skid.
11. Install proportioning valve in master cylinder and hand tighten until proportioning is fully installed and O-ring seal is seated into master cylinder. Then torque proportioning valve to 40 Nm (30 ft. lbs.).
12. Install brake tube on proportioning valve. Torque tube nut to 17 Nm (145 inch lbs.) torque.
13. Bleed the affected brake line.