Has anyone had any incidences of what appears to be a venting noise after stopping the engine. The noise sounds mechanical and lasts for just a second or two but continues intermittently for quite some time. I was told to open the fuel tank cap to release tank pressure. This works for a short while if the tank is just opened and then closed, the noise starts again after a while. To eliminate it completely I've found that if I open the fuel tank and leave it open for 45 minutes no further noise occurs.
What is this all about? Is there a pressure relief valve somewhere that's not effectively releasing fuel tank pressure after stopping?