I may have mentioned this before. When it's hot outside vapor? is escaping thru the gas cap and whistles for a few seconds and then stops. Then it repeats all day. If I open the cap I hear a whoosh and the whistling stops. I've tried silicone spray on the gasket, cleaned the gasket and lubed it but still it whistles. I've raised the tank but haven't removed it but didn't see any reason why it would whistle. Am I going to have to remove it and locate and replace any and all vent hoses to cure this?