Burping gas cap

1997 Ford Explorer Sport

Ever hear of a burping gas cap? Mine burps at regular intervals while running. Meaning, the spring and seal are bouncing rapidly against the filler tube opening. Sounds like burping. Do I just need a new cap or is there something more to this?

Edit: the intervals are based on the amount of fuel in the tank. The less fuel, the more often it burps.

Something may be wrong with your fuel tank vent system. But replacing the gas cap would be a cheap first try. Is your check engine light on?

No CEL. Its been burping for 2 years and I’ve just used it as a joke so far.

Don’t know if it helps, but the burping is pushing air out of the gas tank.

Gas evaporates and creates pressure inside the tank, which needs to be released. You may need a fuel tank vent valve or seal.

I had a RAV4 that did this routinely. It seemed to be the result of warming fuel (putting car in a basement garage warmer than wherever it had just been).
I ignored it.

If you have no CEL…then just challenge the cap to a burp-off and see who wins…or see who can guess exactly when it will have indigestion again. Could be an actual game, but if there is no CEL then all is well. Dont change a thing.

1 Like

Most of the gas caps I’ve taken apart (to see what’s inside) have a spring loaded valve that opens if gas vapor pressure becomes more than the spring’s closing force. That’s a fail-safe mechanism, shouldn’t ever open in normal circumstances b/c the evap system is supposed to prevent any pressure build-up. I presume some sort of over-pressure in the gas tank is what’s making the noise. I’ve never heard anything like that on my cars, but it may just be normal for that particular vehicle. If there’s a problem it would probably be either the cap itself, the fuel tank’s vent valve, the evap canister, or the purge valve. On newer vehicles all that stuff is usually tested during each drive cycle by the computer’s evap software, so check for any diagnostic codes. If no codes, either try replacing the cap, or as long as there are no other engine performance symptoms, just live w/it until/if some symptom develops.

This is great stuff, I guess vehicular indigestion is it. Maybe it will be a great conversation starter.