AIR LEAK ON CRAFTSMAN AIR COMPRESSOR, 3HP,25 GAL, HORIZ TANK

The needle valve that you see is the unloader which releases air pressure from the discharge line after set pressure is obtained. If air continues to leak after the compressor shuts off, the check valve installed in the tank is leaking air out of the tank. Follow the air discharge line from the compressor to the tank. There you will find a brass valve which is the check valve. Simple test is to remove the smaller airline (1/4") from the brass valve and check for air leaking. If leaking remove brass valve and check for debris under the white seat. If you cannot clean the valve, replace with generic check valve from www.grainger.com. It will cost less than factory part. Just order the valve considering the fitting sizes that you need. For exact replacement,( www.sears.com parts). If you sears model # begins with WL then your compressor is made by campbell hausfeld and parts may be ordered from www.chpower.com. Good Luck with you repair and email if you have more questions.