Proportioning Valve

NOTE: It is not necessary to remove Hydraulic Control Unit (HCU) from vehicle to remove proportioning valves. DO NOT disassemble proportioning valves.

Road test vehicle to determine faulty proportioning valve. Remove the suspect proportioning valve from the HCU. Refer to the PROPORTIONING VALVE IDENTIFICATION table. Using fitting with correct thread size, install Pressure Test Fitting (6805-1 or 6805-2) into outlet port of HCU. Install proportioning valve into pressure test fitting. Install Pressure Test Fitting (6805-3 or 6805-4) into outlet port of proportioning valve. Install brakeline to pressure test fitting.
Install a Pressure Gauge (C-4007-A) into each pressure test fitting. Bleed pressure gauges to remove trapped air. Have an assistant hold brake pedal down to obtain reading on valve inlet gauge. Check reading on outlet gauge. Compare readings to specification. See BRAKE PRESSURE table. If readings are not as specified, replace proportioning valve. Bleed affected brakeline.

PROPORTIONING VALVE IDENTIFICATION

Application

⁽¹⁾ Split/Slope

Identification

14" Wheel Disc/Drum

500 psi/.43

⁽²⁾ *

15" Wheel Disc/Drum

500 psi/.43

⁽²⁾ *

⁽¹⁾	Split point is when proportioning valve changes rear brake pressure to prevent skidding. Slope is pressure differential (percentage ratio) between front and rear brakes.

⁽²⁾	Bar code label.

BRAKE PRESSURE

Body/Inlet Pressure

⁽¹⁾ Split/Slope

Rear Brake Outlet Pressure

1000 psi

500 psi/.43

600-700 psi

⁽¹⁾	Split point is when proportioning valve changes rear brake pressure to prevent skidding. Slope is pressure differential (percentage ratio) between front and rear brakes.