Original post by: Chris Wilson ,
My air dryer started blowing off like that and it turned out to be the unloader valve in the head of the compressor. Not a bad job to change at all. There is a little oval shaped plate on the top of the head of the compressor with a torq screw it it. Remove the screw and the plate, then remove the unloader. Its basically a plunger with 2 o-rings on it and a spring on the bottom. Check to see that the o-rings are not damaged, and that the spring is not broken or gummed up. The gasket on the oval shaped plate can also fail, letting air leak out there.