My 1998 cavalier is making a hissing noise at the fuel tank, does anyone know what that would be?

Question

I can really hear the hissing noise under the car and releasing the cap didnt help?

Answer 1

DO NOT LIGHT A SMOKE OR EXPOSE IT TO A FLAME, you could have a fuel leak, Very Dangerous!

Answer 2

Yeah just pressure building up as it gets hot, and the fuel turns to gas and occupies a larger volume.

Alot like a bottle of Coke. Should be safe to leave, if you get worried just release the cap and all pressure will go.

Answer 3

Sounds as if it time for a new gas cap. It is releasing pressure.

Answer 4

its the pressure releasing cus of heat

Answer 5

If its when its running or the key is in the run posistion its probably the fuel pump getting old and noisy. Other then that not sure because the evap system on the car should not let pressure build up.

Answer 6

Is it a humming sound?  That would be your fuel pump, which is normal.

A hissing sound could be a vacuum leak.  Maybe a hose leaking near your evaporative canister.

A release of pressure is normal when you open your gas cap.

That's a few possibilities for you.

Good luck!