.....continue. I concurred with Glenn and thought my new air dryer was defective so I took it back and got another. The new one is kind of doing the same thing but not quite. It charges up to about 125psi, the purge valve spits, then it ticks like a bomb. But the ticking is related to engine speed. The higher the rpm's the faster the ticking and it almost sounds like a machine gun. It will tick until the red needle (what tank is that???) drops to 100 psi, the ticking stops and the compressor kicks in again. This is different form the old dryer (which was brand new) That one would tick and then just hiss air continueously. I did put a new unloader kit in the compressor (with the last air dryer) but I had a small problem with the gasket leaking under the cover. I took it off and sealed it with gasket sealer (I was desperate). I did notice the front piston seemed to be stuck in the hole. The rear one popped up when i took the cover off. This is the AD-SP dryer. Any more help would be appreciated. It is a 98 CH with a 427 by the way. Thanks in advance, Rob W.