HELP!!Fuel Station Tank Venting
We purchased a 2019 in Oct 2018. Recently added, by Camping World, an ONAN generator, great add on. Question, has anyone experienced their auxiliary gas tank "popping" with expansion as the gas vaporizes in the tank? When I say "popping"(deflecting the metal/not sure if the tank is actually bulging) I mean loud enough to hear it 40'-50' away. Visual inspection of the tank doesn't look as if the tank is deforming. I've checked the gas cap venting valve and it appears to be working, put my mouth on it and blew through it, softly and reasonably hard. Obviously this is worrying as I don't need the tank deforming or worse bursting with pressure. Generator runs fine so I don't believe there is a vacuum or that it's not venting, it's somewhat confusing. When I do release the gas cap, slowly, it does vent a lot of vapor. Could the vent flappers in the cap be bad? I contacted Camping world and they assert the installation is correct and vent lines were installed appropriately. Could the cap be defective? Any other suggestions?