Proportioning Valve
NOTE:
Premature rear wheel ABS cycling on a hard brake application may be caused by a defective proportioning valve. Two in-line proportioning valves are used, one in each rear wheel brake hydraulic circuit between brakeline and flex hose. Both proportioning valves must be checked to isolate defective proportioning valve.
- Road test vehicle to determine which rear wheel indicates a premature wheel skid. Raise and support vehicle. Remove suspect proportioning valve from brakeline. Remove retaining clip securing flex hose from bracket so brakelines will not be bent when installing proportioning valve with adapters back into vehicle. See STEP 1 in illustration. See Fig 1 .
- Install pressure Test Fitting Adapter (6892-2) into inlet port and Adapter (8187-2) into outlet port of proportioning valve. Install proportioning valve with adapters back into vehicle. Install Pressure Gauge (C-4007-A) into each adapter. See STEP 2 in illustration. See Fig 1 .
- Bleed air from pressure gauges. Have an assistant hold brake pedal down until pressure on inlet side of proportioning valve is 1000 psi (70 kg/cm2 ) and note pressure on outlet side of proportioning valve. Pressure on outlet side should be 600-700 psi (42-49 kg/cm2 ). Replace proportioning valve if pressure is not within specification. See PROPORTIONING VALVES under REMOVAL & INSTALLATION.
- Remove test equipment. Reinstall brakelines on proportioning valve. Tighten brakeline nuts to 12.5 ft. lbs. (17 N.m). Bleed brake system. See BLEEDING BRAKE SYSTEM . Once brake system is bled, perform pressure test on remaining proportioning valve.