1997 k1500 5.7L exhaust flange leak

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Big nut

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Hey guys I have seen a few threads on here about the leaking dual exhaust pipe flange right after the cats on the 5.7 and I was just wondering if anyone has found an actual solution to the problem.

I was considering welding the two flanges but I really don’t want to pull the pipes off the truck. I was wondering if anyone has welded the flanges together while they are both on the truck?
Any help is appreciated.
 

Schurkey

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My '97 K2500 has a bigass flange between the catalysts. Leaked when I got the truck, leaked after I replaced the gasket/muffler/tailpipe.
www.amazon.com/Walker-31618-Hardware-Gasket/dp/B000CLOS0K/ref=sr_1_1?crid=96QTTWMT1Z2O

The flange was warped. The gasket can't seal the warped flange. Three friggin' bolts to hold about a square-foot of flange. Totally insufficient design.

I considered drilling the flange for an additional fastener. There's room for one more nut/bolt.

In the end, I used an entire tube of muffler/pipe sealer. The stuff is cheap, essentially resistant to heat, and easy to apply to both sides of the gasket. The leak is "mostly" sealed, but not entirely. I live with it.
www.amazon.com/Permatex-80335-Muffler-Tailpipe-Sealer/dp/B000BOAZM8/ref=sr_1_1?crid=3CV5ZXQ1XJ5F6
 
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Schurkey

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Permatex Copper RTV is OK to 700F ("intermittent").

The exhaust flange is directly behind the catalyst. The RTV doesn't stand a chance.

The water-glass stuff I linked-to will take 2000 degrees.
 

Erik the Awful

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I have to admit I did not see that 2000°F rating. I'm going to have to try that stuff out.
 

Big nut

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Thanks for the replies. I have tried the permatex a few times now with no luck, let it dry for a few days and it only lasts around a day or two max I may have to try this water-glass stuff
 
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