Chevrolet Repair: Camaro Question, noise sound, source note

Question
Hi Robert, I have a 1999 Camaro. I am having trouble locating the source of a loud noise in the engine compartment. It sounds like it is related to an air pump and appears to be coming from the rear of the engine. The noise is intermittent and ends before I can locate the source. Note that I can hear what sounds like a air pressure release (tssst) right at the time the noise disappears. Can you suggest what this might be or how I could diagnose which system might be the source?

Thanks, Jason

Answer
Hi Jason... couple of things...check PCV to see if it is venting the block. if you have an air pump on that car remove the belt and see if noise is still there. could be in the control valve. what does the noise sound like before the pressure releases.......hope this helps....merry christmas