You should be able to tell if it's leaking or not by close inspection (looking and feeling). with new parts it shouldn't be hard to prevent or fix a leak. My buddies 85 CJ 2.5 sounds like a diesel also. He does have a cracked manifold but the diesel like noise is mostly because it's old and tired. Wear and tear on the entire valve train can cause it. A rattling/light knocking sound you can ignore or you can consider a partial or complete overhaul. I don't know if that has anything to do with your problem though. <img src="/forums/images/graemlins/cheers.gif" alt="" />