I live in Florida where it does get hot. After driving a while and turning off the engine, I hear a whistle. I opened the gas cap and there was a big whoosh and the whistle ended. Is the gas cap usually venting? Any suggestions on what is happening and how to fix? Many thanks. Jerry

 

sounds like your seal is busted on your cap... my 280zx will go "whoosh" but its not a big "whoosh"

 

there is supposed to be a ventilating system other than just the gas cap. the tank usually holds pressure though.