Exhaust leak

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My Dad passed away and I am tasked with selling his stuff. His 2011 Mercury Grand Marquis with only 37K on the clock has a slight smell of exhaust coming in thru the HVAC right after cold startup. I crawled under there and found a small crack at the seam where the upstream cat joins the pipe to the downstream cat. There is absolutely no rust on this Arizona car (the pipes are still shiny) but it has been in two collisions and I suspect that is how the crack happened. With two collisions plus hail damaged, although all repaired, and a few minor battle scars from the garage door I can only expect to get low wholesale for the car, but I would at least like to try and seal the exhaust leak. Has anyone tried those exhaust bandages, or putty? I cannot get all the way around with a mig gun or I would do that. I saw some putty that says good to 2000 degrees and though I might give it a try unless it is a total waste of time.Miller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:The gray exhaust putty works in a pinch.  Should last long enough to sell and smog if required.  I have some that I used a couple of times now.  It comes in a tin can the size of a hockey puck or there abouts.Lincoln, ESAB, Thermal Dynamics, Victor, Miller, Dewalt, Makita, Kalamzoo.  Hand tools, power tools, welding and cutting tools.
Reply:Thanks, I see the putty is good to 2000 degrees but the epoxy tape only to 800 degrees. I have no idea how hot the exhaust gets right there after the first cat. I can get a stainless band clamp around it as well to help hold the patch on better. It actually looks like one pipe fits inside the other then was welded, and the two cats installed as one piece. I don't want to do a temporary fix that will fail soon so maybe I'll see about removing it and welding if the putty is only a short term fix. I'm not into cheating anyone and will disclose the repair to a buyer.Miller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:Catalytic converters can easily reach 1500F!That is why they are made of stainless steel.I don't see TIG in your tool list!
Reply:

Originally Posted by rexcormack

Catalytic converters can easily reach 1500F!That is why they are made of stainless steel.I don't see TIG in your tool list!
Reply:Get a band type exhaust clamp. That putty is useless, another snake oil ripoff like " seafoam".Miller xmt304,  Miller S22 p12, Miier Maxstar SD, Miller 252 w 30A, Miller super32p12, Lincoln Ranger 9, Thermal Arc 181I with spoolgun, Hypertherm 10000 ,Smith torches. Esab 161lts miniarc.
Reply:Another vote for a band clamp.Something like this:

Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:I think I'd bite the bullet, and weld it.  Clamps still have gaps that gasses can pass through, and the miracle fixes don't work so good.Those CATs get hot enough to start grass fires, if it's dry for extended periods, so you are dealing with a lot of heat in the downstream side of the pipe.
Reply:https://www.holtsauto.com/holts/products/gun-gum-paste/Used these products years ago, stay away from vehicle repairs now. Always had good luck with this brand.Mike
Reply:I never had any success with the putty or the kit that came with a sheet of heatproof cloth, both were completely useless.IMPEACH BIDEN!NRA LIFE MEMBERUNITWELD 175 AMP 3 IN1 DCMIDSTATES 300 AMP AC MACHINEGOD HELP AMERICA!“Freedom is never more than one generation away from extinction.We didn’t pass it to our children in the bloodstream".RONALD REAGAN