Was having a slow leak out of the fill port valve. Took apart and the inside of the valve has a small piston that allows air in and not out. I determined that a small o ring 1x 2.5 metric was the problem. Nothing available locally, so ordered some from the o ring store. After new o ring installed, problem solved. If you have same issue PM me and I can send you new o ring. When ording on line you end up with lots of extras.