Exhaust Manifold Flange Leak

I drive a 2005 Expedition 5.4L 3V Eddie Bauer 4x4.

I have an annoying exhaust leak I believe is coming from the drivers side manifold flange. I know these years do not use gaskets but have the ball-socket type connection.

I recently had to replace my passenger side catalytic converter (including the entire right side of the Y pipe). All 4 manifold flange bolts broke. I was able to use AP StudFixes (imaged below) to connect 3 of the 4 flange bolts. The 4th (passenger side) I had to drill out and use a nut/bolt configuration as the top of the flange is angled.



The drivers side is held with 2 of the AP StudFixes, which is where my leak is. I believe the leak might just be from old warped metal. The leak is only heard when giving it gas, not at idle. I have no interest in replacing said pipe since it’s attached to the catalytic converter and I don’t have the time/money to do this right now.

Can I throw a donut gasket on there to seal it up?? How about using some Permatex Ultra Copper high temp sealant?

Or does anyone else have any good tips for this? Removing the manifold to machine it is not an option either.

Thank you.


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You can try a donut, you got nothing to lose but a little time. I'd stay away from the rtv though, that might make things worse with that kind of heat.

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The copper RTV is specifically for exhaust. It’s rated to withstand 700 degrees. Both the copper and the Permatex Red are high heat for exhaust. The guy that welded up my muffler suggested these two products. He said to put some on the putter edge, let it dry for a while and then plug it up.

The donut gasket probably would be the easiest and cheapest route. Like you said, ain’t nothing but time wasted if it does t work. Do you k ow what size I might need for the flange?


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Jake you asked my opinion. If you already knew, set, and hell bound, why bother asking? Do you question your doctor when he/she gives their opinion. What your doing is a band aid not the correct fix! I'll sit the rest of this post out. We seem to get a bunch of journeyman/ apprentices lately.

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Uh... what?

I literally agreed with what you said, saying the donut gasket would probably be the best first option... along with trying to clarify what the Permatex’s purpose is because it is rated for high heat in exhaust applications.

Thanks for the input though.


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Jake Oleszak said:

Uh... what?

I literally agreed with what you said, saying the donut gasket would probably be the best first option... along with trying to clarify what the Permatex’s purpose is because it is rated for high heat in exhaust applications.

Thanks for the input though.


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Click to expand...

Did you ever find a fix for this, if so what'd you end up doing? I've got the same issue and its been a pain...

Jake hasn't logged in for 3yrs.

When I swapped the factory manifolds for aftermarket on my wife's Monte Carlo that has the same style connection we had a very slight leak. I used a thin and narrow line of copper RTV. It's remained sealed for more than 4yrs now, but that's only ~7k miles as it doesn't get driven a lot.