Do the tires on your car seem to be loosing air but you can't find a puncture? Take the air valve cover off and listen closely for leakage. Even if you can't hear leakage, replacing the schrader valve can ensure that no air will escape through the valve.
The schrader valve is the inside of the actual valve itself. To remove it you will need the specific tool which can be found at any auto parts store.
The tool fits inside the valve and around the schrader. To remove simply unscrew in counter-clockwise rotation until unthreaded.
Drop new schrader in valve and use tool to screw in until tight. I usually say hand tight plus about a 1/2 turn of extra torch.
Be sure to replace valve cover and tighten.
