REMOVAL & INSTALLATION
See Figures 1 and 2Proportioning Valve
The proportioning valve is located on the center of the firewall under the hood. Except for leakage or impact damage, it rarely needs replacement. If it must be removed, all brake lines must be labeled and removed and the valve removed from its mount. Clean the fittings before removal to prevent dirt from entering the ports. After the lines are reconnected, carefully tighten the fittings to 11 ft. lbs. (15 Nm) using a torque wrench with a crow's foot attachment. The entire brake system must be bled.
This check valve allows vacuum to flow out of the brake booster, but will not allow back-flow. This maintains a supply of vacuum within the booster during periods of high manifold pressure. The valve can be removed from the hose by hand. Once removed, the valve can be tested by gently blowing through it. It should allow airflow in one direction but not the other. When installing a new valve, make sure it is positioned so that the air can flow from the booster to the engine. Most replacement valves have an arrow showing the direction of airflow. If in doubt of it's condition, replace it.