hi there new to forum. have had p38 for 6 months and always had this problem and its now getting on my wick. it sits down on ns rear and rises at os front it takes a couple of hours to do this. its got 4 new air springs and new o rings to valve block connecting pipework and there is no leaks. i have heard that it could be o rings inside the valve block, on non return valves or solenoids, please help me before i go to coils.
