When I used to work on these, it first depends on which top hat you have on the valve, PMI had two different ones. Most likely they are the ones with the Allen Screws on them. If so, the top hat is reverse threaded, that would need to come off, I believe it's an oring issue. I would honestly contact PMI about that and have them take care of it. Most of the time it's free of charge except for the shipping of course.