Proportioning Valve (Abs & Early Model Non-Abs)
NOTE:
For proportioning valve testing on Anti-Lock Brake System (ABS), see appropriate
ANTI-LOCK article.
CAUTION:
Not all components use same type tubing flare. Tube leading into proportional valve has ISO flare, while flex hose coming out of proportioning valve has standard double-inverted flare. Use correct adapters when installing gauges to test proportioning valves.
- Raise vehicle. Clean any debris from suspect proportioning valve, connections and area. Remove chassis brake tube from suspect proportioning valve. Remove proportioning valve from rear flex hose (secured by bracket mounted on back side of crossmember). Remove retainer clip attaching rear flex hose from its bracket. See Fig 1 . This should be done to allow proportioning valve pressure test fittings to be installed without bending chassis brake tube.
- Install Pressure Test Inlet Fitting (6892-2) into inlet port, and Pressure Test Outlet Fitting (8187-2) into outlet port, of the proportioning valve. Install proportioning valve and pressure test fittings, as an assembly, back into chassis brake tube. Connect Pressure Test Inlet Fitting (6892-2) onto chassis brake tube. Connect Pressure Test Outlet Fitting (8187-2) onto brake flex hose.
- Install Pressure Gauge (C-4007-A) onto each pressure test fitting. See Fig 2 . Bleed any air out of system, including hose between pressure test fitting and pressure gauge. See BLEEDING BRAKE SYSTEM .
- With an assistant, apply pressure to brake pedal until reading on proportioning valve inlet gauge is 1000 psi. Then check reading on proportioning valve outlet gauge. If outlet pressure is not 525-625 psi, replace proportioning valve. If pressure is within specification, go to next step.
- Remove pressure gauges from test fittings. Remove proportioning valve and pressure test fittings from chassis brake tube and rear flex hose. Remove pressure test fittings from proportioning valve.
- Install rear brake flex hose into mounting bracket using NEW retainer clip. Install proportioning valve onto rear brake flex hose, tighten to specification. Install chassis brake tube into proportioning valve and tighten to specification. See TORQUE SPECIFICATIONS .
- Bleed affected brake line. See BLEEDING BRAKE SYSTEM . On non-ABS vehicles, repeat previous steps for other proportioning valve. If no problem is found with proportioning valves, check rear wheel brake shoe linings for contamination, and ensure rear wheel brake shoes linings meet OEM material specifications.
CAUTION:
Be sure pressure test fittings being installed into proportioning valve have correct thread sizes for installation into proportioning valve, and installation of chassis brake tubes.