For as long as i've owned my car whenever i loosen the gas cap off it depressurizes(makes the same sound as when you open a can of pop.) I was filling up and a buddy if mine that owns a 95 Camaro swears his car never made a sound like that and thinks its bad that the gas tank is building any sort of pressure. I have never given it a second thought, but now i've got the what if syndrom, so is pressure in the gas tank like that a common thing? Or bad?

 

happens to me too, I don't think it's anything to worry about.

 

both my 95 z and my 95 3.4 fire chicken do it .

 

it's one of those things thats been around forever. even my 83 and 84 thirdgens do it.. Supposedly there is a one way check valve in the fuel tank that is supposed to vent pressure. when it quits working or gets stuck it no longer vents.

 

my 94 z28 does it.