Having been told by my local garage my compressor is not working properly. The pump is giving some air but it is taking a long time to fill the system. I have stripped it and checked the seal. It does not seem too badly worn, but the cylinder fell easily from the piston when I took the the long securing out. It seems to me that there should be some friction present - sufficient to hold the cylinder in place when the unit is inverted. Am I correct in these thoughts and should the seal be replaced?