I went for a drive today and after parking the car in the garage I heard a hissing sound. I thought that I had a punctured tire but after closer inspection I found that the sound was coming from the gas tank filler neck...or around there. I took the tank cap off and let the pressure escape and the noise stopped. How much pressure builds up in the tank and is that normal? Just wondering because I had never heard that much hissing before? Thanks

 

There's a gas pressure relief valve mounted under the car next to the gas tank.

 

Oh, that would explain the hissing. Thanks for clearing that up for me OBE1 95Z28 !!