The valve stem is one of the most vital components of your car's safety equipment. Failure of the valve stem will allow a tire to deflate. Sometimes this process is sudden, sometimes it is more subtle. Either way, a leaky valve stem endangers you, your passengers and everyone on the road with you. Determining the exact location of the valve stem failure and stopping the leak only takes a few minutes, the right tools and a bit of knowledge.
Lay your tire onto the ground with the valve stem up. Remove the valve stem cap and set it aside.
Fill the tire with air. Press the tire inflation fitting on your compressor hose onto the valve stem. Pump air into the tire for 15 seconds, remove the fitting and check the air pressure in the tire with your tire gauge. Continue until the tire has 35 psi of air.
Soak the valve stem and valve stem housing with soapy water from your spray bottle. Observe the area for signs of bubbles caused by the leak. Bubbles in the fill hole of the housing indicate a valve failure. Bubbles from the side or base indicate a housing failure.
Slip the end of your valve stem wrench into the fill hole and onto the head of the leaking valve. Twist the wrench quickly counterclockwise to remove the valve. Discard the failed component.
Place a knee on each side of the tire. Shift all of your body weight to your knees to help evacuate the air from the tire through the open housing.
Slip the replacement valve into the empty housing, narrow end first. Slide the wrench over the head of the valve stem and twist clockwise until snug. Be careful not to over-tighten the stem, which will damage the new stem.
Refill the tire with air from your compressor. Use 15- to 30-second bursts of air to fill the tire to 35 psi. Check the tire pressure between each burst to prevent overfilling and bursting the tire.
Remove the valve stem from the hosing and evacuate the air from the tire. Press all of your weight into the tire through your knees to facilitate the process.
Break the bead of the tire. Hit the rubber of the tire around the edge of the juncture with the metal wheel. Separate the metal and rubber around the entire circumference. Slide the head of your screwdriver into the juncture to gently pry apart any stubborn spots.
Bend the tip of the valve stem sideways so that it touches the metal wheel. Slice through the base of the housing to cut away the stopper inside and the main housing outside of the wheel. Remove and discard both pieces.
Spray the notch in your new valve stem housing and slide it into the stem hole in the wheel. Move the head of the valve stem gently from side to side to properly seat the valve stem housing.
Rub the entire bead of the rubber tire with a wet soapy rag to assist in seating the bead. Refill the tire with 35 psi of air pressure. Add air in bursts after the first prolonged burst that pops the bead into place. Keep checking the pressure to avoid overfill.
Overfilling a tire with air can cause a hazardous or even fatal material failure.