Brake Proportioning/Combination Valve: Description and Operation
DESCRIPTIONThis vehicle uses proportioning valves that are inline with the rear brake tubes. The chassis brake tubes connect directly from the master cylinder or HCU (on ABS vehicles) to the brake flex hose. The brake system uses two proportioning valves in-line with each of the rear wheel chassis brake tube.
The non-ABS equipped proportioning valves are located on the front suspension crossmember in the same area where the integrated control unit mounts on ABS equipped vehicles.
On vehicles equipped with antilock brakes, the proportioning valves are located at the rear of the vehicle. Each proportioning valve mounts directly to the flex hose for the rear wheel brakes and has the chassis brake tube for each rear brake connected directly to it.
For additional information and service procedures on proportioning valves on vehicles with ABS, refer to Antilock Brake System, Proportioning Valve, ABS.
Proportioning Valve With ABS And Non-ABS TLEV:
There are two proportioning valve assemblies used in each vehicle. Due to differences in thread sizes, each proportioning valve has a different part number. During any service procedures identify valve assemblies by supplier part number or the bar code label and stamp identification band.
OPERATION
Proportioning valves balance front to rear braking by controlling at a given ratio, to increase the rear brake system hydraulic pressure above a preset level (split point). Under light pedal application, the proportioning valve allows full hydraulic pressure to be applied to the rear brakes.
PROPORTIONING VALVE APPLICATIONS AND PRESSURE SPECIFICATIONS