Wierd exhaust leak/ticking noise that can only be heard in the car?

[Steve]

My car has a exhaust leak/ticking noise that I can only hear from the driver's seat. I had a leaky crossover but I think I got that taken care of but I still have an exhaust leak type of noise. I put the car up on jackstands and I can't hear the noise from underneath(or at least not over everything else) or under the hood but when I sit in the driver's seat it sounds like the standard issue cracked header. I have removed the header twice and can't find a crack or any carbon trails that would show a leak or anything out of the ordinary. I did the GM Top Engine cleaner trick and I did not see any signs of leaks. The motor is freshly built and has less than 2 hours of run time so I don't think it has any mechanical issues. When I listen under the hood all I hear is the normal valve train noise and the injectors clicking but when I drive the car it sounds like the leak is an inch wide! Anyone any ideas what else I can check? Thanks

Steve

 

[corsair231]

I've had those before. It usually ended up being the manifold to head mating. If you aren't using gaskets try a cheap set of stock manifold gaskets and see if it goes away. If you do have gaskets and they are not showing any sings of leaks then the manifolds are probably cracked somewhere.

 

[87NAT]

That top engine cleaner would surely show a leak. It has worked for me on a few occasions. Are you maybe hearing a loose converter bolt? My friends GN had that a few years back. Sounds like a small tick....

 

[Joe 1320]

I've seen instances where a header leaks only when the car is put in gear and under a slight load. If you are using gaskets and any bolts became loose, it's also possible that the gasket burned though just enough to vent the gases toward the bolt. Sealing that is next to impossible without swapping gaskets.

 

[liquidh8]

I have something similar in mine, I haven't tracked it down yet. New gaskets, no cracks. But I am wiring my lift here soon and will be getting it in the air to check with a stethiscope while running.

 

[Steve]

I took both headers off last night and the headers appear to be sealing well but I did find another leak where the crossover meets the passenger side header. I was pretty sure the sound was coming from the driver side but maybe it was in fact coming from the passenger side but either way I need to get it fixed and then I can see if the sound goes away. I should have bought a new crossover instead of buying a used one from a board member. So far I have had to replace one end due to damage and oval shape and I had to cut the crossover in half and take a section out and reweld it because it was tweaked and would not line up with the headers so now I am going to have to work on the other side! So the $60 I paid for it and now about 4-5 hours of work invested I would have been far ahead to have bought a new one. I should have it back together tomorrow and I post up if the crossover takes care of the noise. Thanks for the advice!

Steve

 

[DailyDrifter]

How does the rest of the exhaust system look? Could it be the speedo cable possibly, does it do it in park or when your not moving?

 

[JDEstill]

I had trouble tracking down the same kind of sound. Never could find it because it only became really audible under load, ie while driving. At idle I couldn't hear it. Turned out to be a leak between header and head. Here is a thread on how I tracked it down. This method worked very well for me:
Exhaust header leak tester - TurboBuick.Com

John

 

[Steve]

I had trouble tracking down the same kind of sound. Never could find it because it only became really audible under load, ie while driving. At idle I couldn't hear it. Turned out to be a leak between header and head. Here is a thread on how I tracked it down. This method worked very well for me:
Exhaust header leak tester - TurboBuick.Com

John

Great idea John! I have at least 6-7 hours chasing this leak and when I saw your post I went out and whipped up a plate and put it on and found the leak in 45 minutes! It turns out that the driver side header is leaking where the tube of the number 5 primary mates to the flange. I was looking for a leak at the mating surfaces mainly but the leak was a damaged header!

 

[JDEstill]

That's awesome! Glad I could help And glad you found it. That was a nasty one to try and find. I bet you'll really like how much better the car runs once it is fixed.

John

 

[Steve]

That's awesome! Glad I could help And glad you found it. That was a nasty one to try and find. I bet you'll really like how much better the car runs once it is fixed.

John

When I removed the header and inspected it I still could not see where it was leaking! There was no carbon trail or anything. I welded the tube to the flange along the area where I could feel the leak and that took care of it and now all is quiet. I checked over the rest of the system with the air hooked up and found a small leak at the header to turbo area and found that the corssover had a small leak also. I took care of the those while I was at it so it should a make huge difference!.

 

[1quick6]

That is a cool diagnosis trick. You learn something new here every day.

 

[JDEstill]

hey Steve, when you checked it did you make a threaded hole in the plate like my picture showed, or did you hook your air up to the O2 sensor bung? I did verify that the O2 sensor bung is the same thread as a big spark plug, so the hose I used to pressure things up (from a compression tester or similar) does indeed screw in there. So no need to make that threaded hole in the plate. Just an FYI to someone else that wants to try this.

John