Proportioning Valve
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1997 Ford Pickup, 1997 Ford F-Super Duty, 1997 Ford Cab & Chassis, 1996 Ford Pickup, and 1996 Ford F-Super Duty. However, it is still accessible from the selected car via links, so may be relevant.
Vehicles use a proportioning valve screwed into rear outlet port of master cylinder. See. Fig 1. This proportioning valve has a by-pass feature. The proportioning valve restricts hydraulic pressure to rear brakes to prevent lock-up. The by-pass feature allows full hydraulic pressure to rear brakes in case of front brake system failure.
F Super Duty is equipped with a height sensing proportioning valve. See Fig 2. Height sensing proportioning valve monitors changes in vehicle height. This valve automatically provides optimum front-to-rear brake balance, regardless of vehicle load. The valve controls pressure to rear brakes by sensing vehicle load conditions through movement between rear axle and body. As vehicle load increases (resulting in decreased vehicle height), higher brakeline pressure to rear brakes is allowed. Valve is located on No. 5 crossmember.
CAUTION:
If height sensing proportioning valve linkage is disconnected, proper indexing will be lost. A NEW sensing valve must be installed. The new sensing valve will have shaft preset and secured internally. If shaft turns freely, DO NOT USE.
Courtesy of FORD MOTOR CO.
Courtesy of FORD MOTOR CO.
CAUTION:
Aftermarket load leveling kits, air shocks or modifications which change curb ride height and/or spring deflection rate provide false readings to height sensing proportioning valve. These modifications may result in unsatisfactory brake performance, which in turn could result in an accident.