I believe I have a vacuum leak and I am looking for some advice on how to track it down. I tried listening for were its coming from but its so loud that its not very effective. I did read about using smoke but not sure what hose to blow it into. I wanted to avoid using starter fluid but if that's the best option I will. I also watched a video about using propane so I might go that route as well. I have uploaded a video to YouTube of what it sounds like. It is VERY loud and annoying. So for a little history on it, I would get this same sound before when I had a leak and when all the coolant drained it would start making this noise so I would know to pull over and let it cool down then add water / coolant and the noise would stop. I used some stop leak before changing my water pump and this sealed it up temporarily which would cause the noise to appear even when I had coolant still in it so I would just drive for a bit and the noise would eventually go away. I recently changed my water pump which fixed all my leaks and now that everything is pressurized, this noise has come back with a vengeance and this time it doesn't stop after driving for a bit. After my Jeep heats up to about 200 I hear this noise whenever I left off the gas. When I press the gas it goes away. I don't get any power loss or misfires or a CEL. I was reading that it could be the throttle body gasket or the intake manifold gasket.

https://www.youtube.com/watch?v=b_mV...ature=youtu.be

I have also attached some photos that I had some questions about.

Is there supposed to be a bolt in the intake manifold in this picture?


Bolt missing?

In this photo, you can see what looks to be rust on the firewall. Does this look like a leak in the intake manifold near the back? I did have some rust in my cooling system from using water. I haven't see any fresh coolant back there so I would think if it was related to this noise I would see something fresh?


Discoloration

 

Are you serious? What about that gapping hole in the vacuum pipe in the first picture? I think that goes to the CCV elbow in the valve cover.

 

Here is a better view of the pipe.

 

HAHA in the first picture that looked like a huge hole.