Pressure Cap: Inspection
Hold the cap in your hand, right side up (Fig 1). The vent valve at the bottom of the cap should be normally closed. The vent valve should open with a slight pull with your finger nail.
Replace the cap for any of the following conditions:
- Rubber gasket has swollen, preventing the valve from opening
- Any light can be seen between the vent valve and the rubber gasket. Use only a replacement cap that has a spring to hold the vent shut.
- Gasket on the bottom of the cap shows noticeable thinning
- Cap has been through more than one engine overheat.