I've fixed 2 easy to find leaks in the air system but there seems to be more that are not so easy. The main one was the trailer brakes. That's good now. The other was the seat. Now with both of those eliminated the pressure leaks down to 4 bars overnight but will stay there indefinetly. I figure there must be a pressure shut off or something that would isolate part of the system. I'm thinking that if I know what and where that is that it might help me narrow down the search. Does it make sense that my truck does this? Thanks!