Because the parts of a proportioning valve cannot be fixed or replaced, a malfunctioning part requires the complete valve to be changed out. Before you take off any brake tubes, press the brake pedal down with the depressor so that the master cylinder does not drain its fluid. Raise the vehicle up on jackstands or a hoist, then clean the proportioning valve and brake pipes to make sure nothing can get inside them. Take out the 4 chassis brake tubes from the inlet and outlet ports of the proportioning valve, then unscrew the 2 bolts that fasten the valve to its mounting bracket and lift it away. Separate the end of the proportioning valve actuator that is hooked onto the isolator bushing on the lever of the height proportioning valve. To install the actuator, fasten its hooked end to the proportioning valve lever, placing the isolator bushing in the hook fully and slide the valve shield between the valve and the mounting bracket. Fix the height-sensing valve to the mounting bracket with 23 Nm (200 inch lbs.) of tightening force and connect the 4 chassis
Brake Lines to the valve's ports, tighten them with 16 Nm (142 inch lbs. of force). Modify the proportioning valve actuator and run the brake bleeder until all the air in the hydraulic lines is out. Next, take the vehicle out on the road and use the brakes to check if the system is running as it should.