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ccriders 03-24-2012 01:58 PM

Exhaust Manifold outlet threads
Had some one work on my A4 exhaust, only to have the lower bolt that holds the flange that connects the dry stack to the exhaust manifold pull out taking the threads in the manifold with it.
Upon inspection I saw that someone previously used a shorter bolt on the lower side than was used on the upper, by about 1/4 of an inch. It appears that the first 1/4 inch of threads came out with the bolt, but at least that much remains in the manifold.
How do I proceed from here?
Worst case is a new manifold and flang, etc.
Next I guess is to remove manifold and have a helix installed.
Last would be to use what is there only get a longer bolt that uses the deepest 1/4 inch of threads. Is this advisable?

Dang, I'm missing some great sailing weather!

sebez 03-24-2012 06:30 PM

Use a helicoil thread repair, it easy, fast and strong

alanr77 03-25-2012 09:29 AM

Re: Exhaust Manifold outlet threads
Another option would be to get a tap and die set (always good to have) and re tap the threads to a slightly larger size. I'm thinking metric. That way the fix is permanent. The only thing you have to watch is the thickness of the material you are tapping. I have always been hesitant to use heli coils on things like exhaust manifold, intake, head or high stress bolts. FWIW. AR

travlineasy 03-25-2012 01:59 PM

Re: Exhaust Manifold outlet threads

Originally Posted by sebez (Post 850149)
use a helicoil thread repair, it easy, fast and strong


Capt Len 03-27-2012 12:52 PM

Re: Exhaust Manifold outlet threads
When I make up a 2 flange exhaust joint I use thru bolts and nuts so this is never a problem.May be difficult to retro tho.

alanr77 03-28-2012 08:47 AM

Re: Exhaust Manifold outlet threads
Unfortunately, on the A-4, the bolts holding this flange do not go all the way through. So you can't use a thru bolt. After looking at the flange on my engine, being that is is a very low stress point, I would imagine heli coils would work. I just always looked at heli coils as a temporary fix.

ccriders 03-31-2012 12:17 PM

Re: Exhaust Manifold outlet threads
After carefully measuring the amount of stripped threads and the amount of good threads remaining, I found that I had almost twice as many useable threads as were stripped out. So, I decided to go the longer bolt route and was able to get enough torque to fully seat the flange against the manifold. I'm fairly confident that this is going to work, but need to get a CO monitor to be sure there are no vapor leaks. The water leaks are stopped.
Thanks for your advice. If I were to go the helix or larger bolt route, I would have to remove the manifold and who knows what that would lead to. KISS.

Capt Len 03-31-2012 10:41 PM

Re: Exhaust Manifold outlet threads
So I thought about a spool made of two matching flanges and a suitable dia pipe (about 1&1/4 " long;weld it up and bolt onto manifold permanently. Exhaust riser thru bolts to other end and can be removed easily when needed. Can change angle of the dangle if that's a help. Just a thought.

mickeyrouse 06-09-2012 01:14 PM

Re: Exhaust Manifold outlet threads
Same thing happened to me. Helicoils, no problem

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