Checking the valve of an air tube or tire (Mercedes-Benz C-Class W202)

1. Unscrew the dust cap from the valve.

2. Apply a small amount of soapy water to the valve. If a soap bubble forms, tighten the valve firmly with the screw-on dust cap.

Caution! Only the metal dust cap may be used to close the valve.

3. Check the valve again. If bubbles continue to form or the valve cannot be tightened further, replace the valve.

4. Be sure to screw the dust cap back on.