Finding an Exhaust Leak
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New User
Joined: Aug 2008
Posts: 2
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From: Quilcene, WA
Finding an Exhaust Leak
I've got a 1974 F-350 Custom (Chinook motorhome!) with a 390... And an exhaust leak. I'm getting gassed out of the cab every time I drive it; I've gotta fix it before I end up with carbon monoxide poisoning... 
There is some visible rust on the manifold and pipes, but nothing really obvious like cracks or gaps. I would prefer to seal the leak for now, as I can't afford to replace the exhaust system at the moment, but I cannot find it. I am starting to think I should just start replacing all the seals.
Any suggestions?
Thanks,
Tristan
There is some visible rust on the manifold and pipes, but nothing really obvious like cracks or gaps. I would prefer to seal the leak for now, as I can't afford to replace the exhaust system at the moment, but I cannot find it. I am starting to think I should just start replacing all the seals.
Any suggestions?
Thanks,
Tristan
Hotshot
Joined: Mar 2007
Posts: 10,101
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From: Pa
An elcheapo way to check for an exhaust leak is a piece of rubber hose. Fish around with one end looking for leaks and put the other end to your ear and listen for leaks. Its a redneck mechanics stethascope. I usually feel around with the engine running for any air/exhaust leaks. You can usually feel even small leaks. If theres a leak at the manifold/header you can usually hear a pronounced "tick". The header bolt came lose on my 74' and I could hear the leak. I'd start at the manifolds and work your way back. Pay extra attention to any welded or clamped joints and gasket areas.
To build some pressure in the system you can plug the tilpipe up a little by holding a rag over the end. May help find the leak faster and see if the system will build pressure when the tailpipe is plugged for a couple seconds.
To build some pressure in the system you can plug the tilpipe up a little by holding a rag over the end. May help find the leak faster and see if the system will build pressure when the tailpipe is plugged for a couple seconds.
Senior User
Joined: Sep 2007
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a "leak" usually wont get so much in the cab, for you to notice.
it might be coming in, from farther back. or theres a HOLE in the pipe..but again, itd prob be further back, and easy to spot.
can you hear it?
just take it in, most shops will check it for a leak for free. and if its a pinhole, or something minor, can just tack it closed.
it might be coming in, from farther back. or theres a HOLE in the pipe..but again, itd prob be further back, and easy to spot.
can you hear it?
just take it in, most shops will check it for a leak for free. and if its a pinhole, or something minor, can just tack it closed.
Hotshot
Joined: Mar 2007
Posts: 10,101
Likes: 40
From: Pa
The older trucks arn't sealed up near as tight as the newer models especially with old worn and cracked weather stripping. My 74' also has two vents that can be opened near the floor (One on each side) if one is open the smell will get right in.
