Proportioning Valve
NOTE:
A premature rear wheel ABS cycling on a hard brake application may be caused by a defective proportioning valve. One proportioning valve is located on each rear wheel brake hydraulic circuit. Both proportioning valves must be checked to isolate defective proportioning valve.
- Road test vehicle to determine which rear wheel indicates a premature wheel skid. Remove appropriate proportioning valve from brakeline. Proportioning valve is located on brakeline, near flexible brakeline at frame rail.
- Perform STEP 1. See Fig 1 . Remove mounting bracket from frame rail and brakeline clamps so brakelines will not be bent. Perform STEP 2. Install Adapters (6892) on each end of proportioning valve and install adapters and proportioning valve back on brakelines.
- Install Pressure Gauge (C-4007-A) into each adapter. 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 on outlet side is not within specification.
- Remove test equipment. Reinstall brakelines on proportioning valve. Tighten brakeline nuts. See TORQUE SPECIFICATIONS . Bleed brake system. See BLEEDING BRAKE SYSTEM . Once brake system is bleed, perform pressure test on remaining proportioning valve.