Grand Voyager V6-3.0L VIN 3 (1998)
Load Compensator: Description and Operation
DESCRIPTION
CAUTION: The use of after-market load leveling or load capacity increasing devices on this vehicle are prohibited. Using air shock absorbers or
helper springs on this vehicle will cause the height sensing proportioning valve to inappropriately reduce the hydraulic pressure to the rear brakes.
This inappropriate reduction in hydraulic pressure potentially could result in increased stopping distance of the vehicle.
Junction Block Location
On vehicles not equipped with ABS brakes, the brake systems Hydraulic Control Unit (HCU) is replaced by a junction block. The junction block
is made of aluminum and is mounted to the front suspension crossmember on the drivers side of the vehicle in the same location as the HCU on an
ABS equipped vehicle. The junction block is permanently attached to its mounting bracket and must be replaced as an assembly with its mounting
bracket. The junction block is used for diagonally splitting the brake's hydraulic system.
Height Sensing Proportion Valve Operation
Vehicles not equipped with ABS brakes use a height sensing proportioning valve. The height sensing proportioning valve is mounted on the left
frame rail at the rear of the vehicle. The height sensing proportioning valve uses an actuator assembly to attach the proportioning valve to the left
rear spring for sensing changes in vehicle height.
OPERATION
The height sensing proportioning valve regulates the hydraulic pressure to the rear brakes. The proportioning valve regulates the pressure by
sensing the load condition of the vehicle through the movement of the proportioning valve actuator assembly. The actuator assembly is mounted
between the height sensing proportioning valve and the actuator bracket on the left rear leaf spring. As the rear height of the vehicle changes
depending on the load the vehicle is carrying the height change is transferred to the height sensing proportioning valve. This change in vehicle
height is transferred through the movement of the left rear leaf spring. As the position of the left rear leaf spring changes this movement is
transferred through the actuator bracket to the actuator assembly and then to the proportioning valve.
Thus, the height sensing proportioning valve allows the brake system to maintain the optimal front to rear brake balance regardless of the vehicle
load condition. Under a light load condition, hydraulic pressure to the rear brakes is minimized. As the load condition of the vehicle increases, so
does the hydraulic pressure to the rear brakes.
The proportioning valve section of the valve operates by transmitting full input hydraulic pressure to the rear brakes up to a certain point, called
the split point. Beyond the split point the proportioning valve reduces the amount of hydraulic pressure to the rear brakes according to a certain
ratio. Thus, on light brake applications, approximately equal hydraulic pressure will be transmitted to the front and rear brakes. At heavier brake
applications, the hydraulic pressure transmitted to the rear brakes will be lower then the front brakes. This will prevent premature rear wheel
lock-up and skid.
The height sensing section of the valve thus changes the split point of the proportioning valve based on the rear suspension height of the vehicle
When the height of the rear suspension is low, the proportioning valve interprets this as extra load and the split point of the proportioning valve is
