The Stovebolt Site Forums The Shop Area General Truck Talk Gasoline boil out of filler neck.?

Any way to prevent gasoline from boiling out of gas cap on a task force truck when left in sun and height temps? I thought the filler neck had a overflow tube to prevent such occurrence ? Would a new gas cap prevent it. Took the two stage paint right off my truck. Tank was not overfilled at time. About 9/10 th full.