Check valve it is. <br/> Determine due to lack of external leaks. It was leaking back upstream. Thanks for the tips. <br/> Sorry. This post was supposed to go onto the end of my air question. <br/> FWIW found a complete check valve on E bay for 16$, <br/> 52 $ for the same at NAPA. <br/> and the repair kit at" find it parts". We'll see if it is correct . RN10y Haldex