There are different "flex joints" in a car — suspension, exhaust, drivetrain. It would help if you describe the specific part or if there another name for it.

Or tell us what it is in the parts catalog: http://www.realoem.com/bmw/enUS/part...-Mini-Cooper_S

 

Must be the flex joint at the header.

 

 

Only real fix is the TSW or VibraTechnics upper motor mount, both will give you more vibration in your steering wheel, the VibraTechnics will give you the lesser of the two.

 

He said he changed the motor mount (I presume with OEM). If a new OEM mount isn't sufficient to prevent a flex joint from breaking, the problem is probably more than just the engine mount.

Which mount(s) did they replace? The engine has an upper and lower mount, and there is a transmission mount.

 

Going to move this to the Stock Problems/Issues area.

The question I have is how was the joint replaced as the different thicknesses involved have to be welded correctly.

 

I would not assume the OP's car has the stock header as he provided next to no specifics. For all we know the car could have suffered from too much performance muddling. Stock motor mount, however crappy you'd like to slam it, cannot explain two rapid failures. The header could have been de-catted, or worst not enough or too much length for the flex joint to function, or the replacement flex joints are simply crap. Too many unknown to give advice.

 

I had the issue of the flex joint cracking on my 06 JCW, mostly due to heavy throttle inputs associated with autocross. The constant engine loading - unloading caused by repeated throttle inputs caused the flex pipe to crack. I finally got rid of the problem by installing Powerflex inserts for the transmission and the rear engine mount, as described here: http://www.billswebspace.com/MiniPow...ansInserts.htm


Got a bit more NVH at idle, mostly when the A/C compressor turns on, but nothing that bothers me too much. I'm still running an oem front engine mount

 

The extremely quick failures of your repaired exhaust system could indicate a poorly done or inadequate repair.

I recently did a Vibratechnics top mount and a BSH lower mount and it significantly decreased the amount of thrashing around the engine does. I would highly recommend it if you are unhappy with that aspect of the vehicle. It is not outlandish to think that the engine movement can fatigue exhaust parts over a long period of time, but would not have caused your two rapid failures.

Disclaimer: I am not a mechanic, my suggestions will not fix your problem, and I am not legally liable for the decisions you make on your car.

 

So we have a owner with the second flex joint destroyed within 10 minutes of install, some are giving the advices that a set of aftermarket motor mount and lower damper (not ) will cure the ill. My advice to OP is try to determine if the flange position of the header WRT that of the catback has been significantly altered, due to a number of possible reasons. It may not be easy if he does not wrench the car himself. The failure is very likely due to the joint being stress beyond its designed (if there were design done ) operating range and/or angle.

The second possibility is plan crap flex joint used, which I suspect is less likely as it lasted 10 minutes. Even one made of baking foil may last longer.

Post some photos!

 

It's not unreasonable to think part of this problem could be related to engine and trans movement as a result of bad engine mounts. So suggesting to the OP that looking at replacing those inadequate mounts as part of a solution is not really that wild of an idea.

 

Only if OP complains his flex joints dies in say < 30-40 k miles. Not when it fails within 10 minutes. All movements are bad for the exhaust system, but no movement, while best for the exhaust, is bad for your peace and comfort so you have to choose the right compromise, and I know where yours is.

My point is overzealous touting of what I chose to upgrade does nothing to help OP's problem.

 

OK

I'll be done here, you've made your point. I'll edit my original post, wouldn't want someone to look at options for upgrading poorly designed parts...

 

How did the first and second flex joints break? Is this on a stock header or aftermarket? As other have asked, when they replaced the mounts did they do the upper, lower, amd transmission moints?

By chance do you know if you have a cross brace like this TSW Cross Brace ? There are other posts about the possibility of damaging the flex joint if not aligned correctly or modified.