So I took off my intake manifold to track down a fuel leak on my 97 E300 Diesel. I fixed the fuel leak and as I was cranking the car to move fuel through the shut off valve (so I could check if it was still leaking) I noticed out of ONE of the valves air was coming out with pressure. It's the intake manifold so air should be going in right, not coming out. Any ideas on what this could be? I'll take a picture of the valve tomorrow morning and post it also.