Catalytic converter broke off rear flange

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What caused this? Could this be welded back?
Any help is greatly appreciated.

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I see one hang point already, so chances are others rusted trough and broke off as well, putting a lot of bending stress at this point.So with stress, heat and rust, it broke off.
That flange would have to be unbolted from the exhaust and maybe then it could be welded back. But this is out of my experience.
 
cant really weld rust..and its rusted thru..

Take a look downstream and make sure that the pipe isnt hitting suspension causing the bind.
 
Stainless steel is much less prone to corrode. However, it will corrode and fail, especially when heat is involved.

It "rusts" differently than steel and often the smallest of pits result in component failure due to unseen, intergranular corrosion.

Bottom line, your CC has corroded to the point of failure.

I could weld that back together with a TIG welder and some 321 stainless rod. However, it will fail again due to the above mentioned condition.
 
Too thin and rusty to effectively weld that cc. Aftermarket ones aren't too expensive or you could go to a junkyard and hope to find a decent one.
 
The junkyards I deal with wont sell a used one. A small private yard may sell you one for scrap,for testing only if they know you. AFAIK its illegal unless it is recertified and the fine is pretty stiff if its not. Ebay would be a more likely place from a private person.
 
Has anyone ever seen a rusted out cat? I thought they got hot enough to burn off any moisture that would cause rust through.
 
If it makes a difference OP, you're fortunate to have a flange with a nut and bolt setup rather than a bolt threading into the flange itself. That means you can just whale on it and break the bolt to remove it, just replace the bolt. If it were one of those setups like where there's a spring bolt that threads into the actual flange, that's a risky proposition if you break the bolt because the remaining portion is still threaded in. If it were me I'd just torch these free, if not break the bolts in this situation and replace them in a heartbeat.

Originally Posted by dishdude
Has anyone ever seen a rusted out cat? I thought they got hot enough to burn off any moisture that would cause rust through.

I have, the Altima I junked had an exhaust system that was rotten. The catalytic converter looked exactly like this one down to the color and texture of the rust LOL. The heat shield that was originally spotwelded on had long ago rusted off and disappeared leaving the shell to be battered by the elements and eventually rust through, leaving holes in the shell. I found the holes because there were soot marks indicating where the exhaust was leaking.

In my case I caught it before it broke off completely like the OP's did. On mine they had a bracket with two hangers attached to it that sits between the flange of the exhaust and cat, that bracket had completely rusted away so there was already stress on my exhaust.
 
OE is generally 400 grade stainless like magnablow uses longer life but unlike costlier 300 series that lasts forever + sometimes manufacturers think my uncles dodge with the great cummins diesel pipes were good but all the hangars rusted off!! may as well get a new system as it will likely continue with issues + aftermarket will generally cost less!! cheaper 400 grade stainless is said to form a protective outside layer that looks like rust but is said to be protective corrosion, i call bull on that. 200 thou + 10 years in pa salt + my 2001 jetta's 304 stainless system was only discolored, not OE but a magnet tells me some of it was 300 series but small + restrictive, hence my bigger aftermarket 304 stainless system!
 
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Originally Posted by dishdude
Has anyone ever seen a rusted out cat? I thought they got hot enough to burn off any moisture that would cause rust through.


It's probably almost unheard of in Phoenix. But in an area that uses salt on the roads in winter, and people neglect to wash the salt off the undercarriage regularly, it's pretty common.
 
A little over a year ago, my OEM exhaust mid pipe corroded in half at the flange joint near the front of the muffler with my '03 Corolla. I wanted to remove the front half exhaust pipe via the up stream flange joint so I could try repairing in open space. No way as it would have created more problems doing so. For example, those rusted fasteners in your pic will likely put up a fight and snap and you have to either drill it or torch it out etc. etc. Too much work. I bought the FCAW from harbour freight and welded the corroded joint back together.

I did not expect that it would work but risked ~$175 just to buy the equipment and tried it out. I hung the exhaust back under the car and carefully butted the two pieces to where they were mated originally by eye to minimize gaps and just welded at the lowest voltage and various wire feed rates until I was able to mend the seam together. Yes it was God awful butt ugly and then I further reinforced and filled all the nooks and crannies with jb weld.

Not saying this is how you should do it but fortunately my efforts worked temporarily and if the joint broke today...then so shall let it be. So anything is possible as long as you're realistic about the outcome. You may have to remove the O2 sensor first and see how to get access but in my case, I was not going to spend a fistful of money until I absolutely looked into every cheap methods to do this.

Best of luck.
 
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