New exhaust flange?

I've been chasing leaks at the flange between the rear cat and muffler for months, heck years, now. Muffler and centerpipe are brand new (1 year old). Cats are still good as far as I know. The CEL comes and goes. I've replaced the gasket a ton of times, can still feel leaks from time to time with my hand. The flange on the cat is very very rusty, to the point where it bends quite a bit when I tighten it down. Therefore, I am not getting a good seal at all. I tried putting on high temp JB weld to fill in some of the recesses and create a better mating surface but it just fell off after a while and lo and behold leaks are back.

Good news is the light did go away long enough for me to pass inspection lol.

So I was thinking two things. Just welding a bunch of filler onto the rusty flange surface then grinding it flat. Or cutting the flange off and welding a new one on. All of these repairs are gonna need to be done on the truck because if I take off the cat then I'm gonna have the same issue with the rear cat lol and I may as well just replace both cats. Any advice? Does anyone know where to get a weldable flange, I don't have the means to make one?

 

If you plan to weld another flange on why not just cut out the flanges and weld the pipes together?

 

I bought them using part numbers from Walker Exhaust .

Either from Summit or Amazon I don`t recall

 

A muffler shop can cut out a good flange from a spare pipe and weld it to your pipe.

Cheaper option would be buy some sealant like this one. Use it with your flange gasket.
Permatex 81878 Ultra Copper Maximum Temperature RTV Silicone Gasket Maker, 3 oz. Tube

$9 Permatex 81878 Ultra Copper Maximum Temperature RTV Silicone Gasket Maker, 3 oz. Tube

https://www.amazon.com/dp/B0002UEOPA/ref=cm_sw_r_cp_api_i_FOH-CbF5ZSVNZ

 

There aren't any muffler shops within an hour or more from where I live. I've seen some flanges on ebay but not it's hard to tell what is the most similar. Plus, most of them are stainless steel which I won't be able to weld to the existing steel pipe.

 

Are you up in the Northwest Corner of NJ??

Permatex #2 is good for sealing Exhaust leaks

Just for the information you can weld a Stainless Flange to mild steel pipe or the other way I do it all the time

I will look see if I can find a Part number

 

I second that. I use to work in a fab shop. Welded SS to mild steel many times with a MiG welder.

 

Western Central or Northwestern NJ yeah

 

I cut my flange off and used a piece to connect the two pipes. had to use a band clamp to cover one section as it did not pass inspection due to me not using a 2nd clamp since it was ultra tight when first put in

I believe I used a short (or cut it down) 2" (or 1.75 can't remember, was due to the CATs flaring) round exhaust section and slid that over the length left from the cat and then slid the other end inside the "mid-pipe"

I may have to get a more permanent fix next year but we'll see

 

I’ve been bouncing between different “temporary” fixes and every year the light comes back after a new leak forming. Definitely looking for more of a permanent fix at this point.

 

Super glue two gaskets together just enough to hold them together then use permatex #2 might work for some time.

What also happens is the part of the exhaust pipe extending through the flange rusts off so the gasket slides around just enough to cause things to leak.

thermal cycling causes all sorts of interesting things

might be time to install some new exhaust

 

You can try some simpler things:

1. Cut out the bad flange and replace with a suitable combination of double female couplers, pipe and clamps from auto parts store.
2. I got a metal composite gasket material in sheet form from Napa auto parts. It has some type of high temperature core material with thin textured metal on both sides, ask the counter man. You can make a gasket out of that and see if it lasts better. That is made for exhaust systems.There is no sealer that I have had any luck with. They burn out or get too hard and fall out.
3. Clean up the flange and braze together in place to seal the leak if you have the equipment. I think any repair shop with a torch can do that.
4. Make sure all hangers are good and in place and/or add an extra if needed to limit movement of the exhaust system.
5. Dumpster pick flanges from a discarded system and use with coupler/clamps for your repair parts. I see exhaust systems in garage dumpsters all the time. Make a gauge out of wood with a slot that matches your pipe O.D. Then you can find a close match from used parts. Bring a hacksaw with new blades.

Good luck with it.