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Old 06-06-2019, 08:02 AM   #1
Steiner
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M20 Downpipe Flex Joint Repair?

I have a 1990 325ix that has developed a leak at the downpipe flex joint. The leak is actually on the bottom of the flex joint where it welds to the pipe. The cat has been removed from this car by a prior owner.

A mechanic attempted to repair the pipe, but the repair did not last. When I took it back to him to look at, he stated the pipe (not the flex joint) was too thin to weld and that I would just have to get new downpipes.

Sooooo..... is he right? Or, is there some sort of repair I can do to replace the flex joint that will actually weld to the pipe? I'm open to suggestions!
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Old 06-06-2019, 08:12 AM   #2
nrubenstein
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He probably said that the flex joint material is too thin to plausibly weld. The pipe itself is perfectly weldable.

Just get a new flex joint and have it welded to the pipe.
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Old 06-06-2019, 08:47 AM   #3
Steiner
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Quote:
Originally Posted by nrubenstein View Post
He probably said that the flex joint material is too thin to plausibly weld. The pipe itself is perfectly weldable.

Just get a new flex joint and have it welded to the pipe.
I thought the same thing, so I asked him about just replacing the flex joint. He was very specific - and I made sure to ask - that the pipe was too thin to weld, not the flex joint. Frankly, it didn't make sense to me either.
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Old 06-06-2019, 09:10 AM   #4
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Quote:
Originally Posted by Steiner View Post
I thought the same thing, so I asked him about just replacing the flex joint. He was very specific - and I made sure to ask - that the pipe was too thin to weld, not the flex joint. Frankly, it didn't make sense to me either.
He may just not have access to acceptable welding equipment / skill.

(Although what that lack of skill may be, I don’t know. Novice welder me could do it, and an M20 midpipe was one of the first things I ever welded.)
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Old 06-07-2019, 07:35 PM   #5
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Don't rule out the possibility that being in MI the pipe could be corroded to the point of being too thin to weld
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