The check valve is a small, inexpensive component; but, it is a vital component of an automobile power brake system. The check valve is a one-way valve that allows air to be sucked out of the brake power booster, but does not allow air to flow back through the check valve and into the booster. This is a critical safety feature of the power brake system, in that it ensures the booster will have enough retained vacuum for two or three applications of the brakes, even if the engine suddenly stops. Testing the operation of the booster check valve is not a difficult task and can be completed at home.
Instructions
- 1
Park the automobile on level ground. Open the hood, and find the vacuum booster. It is a round, somewhat dome-shaped contraption, mounted to the rear wall of the engine compartment, more-or-less in line with the brake pedal. It should be near, and a bit below, the brake fluid reservoir.
2Find the vacuum hose that runs from the engine to the vacuum booster. It is normally a black, rubber hose approximately 3/4-inch in diameter. Follow the hose to where it connects to the engine intake manifold. Disconnect the hose at the engine, by first removing the hose or clamp that holds it in place, using pliers or a screwdriver. Slip the hose off the nipple. This will probably require some wiggling, twisting and pulling, as the hose will have a snug fit.
3Insert the turkey baster into the hose end, and push it in, to seal it. Squeeze the baster, to force air into the hose. If the booster check valve is working properly, you should not be able to force air through the check valve into the vacuum booster. Unfortunately, a blocked vacuum hose will have the same effect. Remove the baster from the hose.
4Squeeze the baster bulb, insert the baster into the hose end, and push it in, to seal it. Release the bulb, to see if it will suck air out of the hose. If the vacuum hose is not plugged, and the booster check valve is working properly, you should be able to easily suck air out of the vacuum booster.
