You have to supply a constant 5psi flow through the system . I fill my compressor tank with 150psi then turn it off . I set the regulator to 5psi and attach the hose to my leak tester . I added an inline gauge to my tester to see what was happening right at the attachment . If you just put in 5psi and cut off the air supply the air will leak out in a matter of seconds as it bleed out around the piston rings . thats why you need a continual , regulated 5psi of air moving through the system to keep up with the air thats escaping . You will hear alot of air moving through the system and even hear it coming out the oil fill hole , this is normal . if you think you hear a hissing sound somewhere then put your finger over that area and see if the sound changes or if you can feel it . If your still not sure spray some soapy water on it and look for bubbles . After you fix/replace the broken bolt on the upper plenum just remember that during this test you will hear air moving through and making noise in that middle plenum area . Hope this helps .
