air compressor check valve help

[sweetk30]

helping a friend fix his kobalt compressor . when it shuts off its leaking air from the unloaded hose at the pressure switch . pressure switch is new and still does the same . he figured the pressure regulator he had on the out let was bad and got a new one still same thing no leaks until compressor shuts off .

is my thinking correct the tank inlet check valve has gone bad ?

 

[The Cobbler]

easy to check. if when the compressor is not running , if the unloader keeps bleeding ... you have a bad check valve
You've diagnosed the problem I'd say

 

[dogdog]

Take out the check valve and dump in ultrasonic cleaner with just degreaser or water run it a few cycles might clean it enough for the check valve to seat proper. Did that for two craftsman oil-less and worked a lot better from one day leak down to a week