The compressor governors are cheap as dirt.I bought a new one a while back for $15.A common cause of pressure loss is the brake valve,with air going out the exhaust.Simply depress the pedal fully,and the valve will seal,while pressure builds up.For air leaks,soapy water is your friend.Put some in a spray bottle and go around the entire air system.Dont overlook the tractor protection valve inside the rear chassis.Hook up the air system to a full pressure workshop compressor,pressure will often cause the problem component to seal.Unfortunately,kits for the Mk3 type brake valve are obsolete.The Mk4 treadle valve is available.Regards John.