How to seal exhaust leaks?

[dmention7]

Okay, so I installed my catless midpipe this weekend, and it went relatively smooth, save for a medium-sized exhaust leak where it joins up to the crappy catback that was installed on the car when I bought it. The flanges don't line up quite exactly enough, so even with a new OEM gasket, and the bolts (it's a 2 bolt flange) tightened down as much as I can, there's still a pretty good puffing of air coming out of the bottom side of the joint. I even tossed in a couple of large washers to try and distribute the bolts' clamping power over as much of the flange surface as possible, hoping it would pull the bottom edge shut tighter.

Anybody know of a good way to seal up a leak like that? I mean, this thing is going to be loud enough as it is without the exhaust leak... lol

Maybe I'll just have an exhaust shop weld up the joint?

 

[AJ]

So each section (where it connect to the other flange) has some material that blocks a good seal? Anything you can take a dremel to to get more of a flat surface?

 

[micahlarson]

jb weld!!!! SOLDER! .... no.. just kidding..

 

[dmention7]

Honestly, I'm not exactly sure what is causing the surfaces not to mate up flush--it looked like they should mate up well, but I think the flanges are just not quite angled correctly to meet up flush. I don't think there is excess material on the flange surfaces--I'm pretty sure the welded sections of pipe were recessed behind the flange at all points in order to accommodate the gasket (one of those donut type buggers).

One possibility that just occurred to me is that the flange on the catback might be slightly bent--so it's not a perfectly flat surface. That joint kept coming loose before, and maybe the periods where it was loose allowed for a bit of flex, and the flange got a bit warped...

I'll take a closer look later on, but I just wanted to get the damn thing in there, and get out of the heat... took way longer than it should have, including a couple trips to the hardware store for bits and pieces I thought I already had.

 

[micahlarson]

keep us posted

 

[mndsm]

Set something flat against it while under the car. a book or something, or a piece of wood. You could probably see where it's warped if anything.

 

[dmention7]

Yeah, a bit of googling informed me that there are a couple of different products that might work out for me. I'll probably swing by Checker or Napa after work and see what they recommend.

 

[JustROLLIN]

Have someone straighten or increase the radius of the bend.

 

[dmention7]

I ended up with a product called Muffler Mender. Unbolted the joint, and slathered it all over the flanges, including where the gasket seats. Bolted everything back up nice and snug, and let it dry overnight. A couple days later, and all is well!