'97 ECSB 5.7 Vortec exhaust flange leak

GL1500 · Sep 8, 2016

Over the last week or so, I noticed a leak in the connector flange gasket. This is the strange shaped double-pipe flange connector directly after the cats. I removed the old one, scraped the remaining gasket as well as possible (including a sharpened chisel) from each side. I couldn't get it completely clean, meaning there were some areas with only the facing of the previous gasket. I would guess less than 1/16" thick. A file wouldn't touch it, nor would a sharpened chisel. There's not enough room to get my grinder in there with the crossmember in the way. When I installed the new gasket and tightened the 3 nuts, it's still leaking pretty much all the way around. It's about as tight as the nuts will go without breaking the studs, and the nuts are tightening down all the way.

If I were to add another gasket, would it likely seal up? I'd be doubling the gasket but I'm not sure if they would compress enough at the studs and any high spots to allow this to work.

Thoughts?

Thanks,
Steve

GL1500 · Sep 14, 2016

I'm sure I'm not the first to run into this problem, was hoping I could get a little advice on how to fix the leaky gasket issue. Today I stopped at the auto parts store and one guy said the connector flanges warp causing the leak and that people double, triple, up to six gaskets to fix it. At $16 each I don't mind putting a couple on it but even if it does seal up it seems like a temporary fix. Another said to use 2 gaskets and coat each side and in between with a heavy coat of muffler sealant.

I did pick up another gasket and some of the muffler sealant but it seems like a crapshoot as to whether it will work even short-term.

Any advice GREATLY appreciated.

Thanks,
Steve

Jrgunn5150 · Sep 14, 2016

I don't think stacking gaskets is going to work long term. I've only ever tried it once, on some cheap headers. It worked for like, not even 100 miles.

My advice, if it just drives you nuts, is to cut that flange out and replace it with something else.

MDR-97-Z71 · Sep 16, 2016

Had the same leak in mine, best solution is to cut it out and add pipe in place of it

Sent from my powered iPhone

superdave · Sep 16, 2016

Had that issue with mine after putting on my headers. Another new gasket with Permatex ultra copper max temp silicone (or something like that) fixed it right up. I just think it's damn near impossible to get that surface flat.

GL1500 · Sep 26, 2016

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Just an update. I ended up using a new gasket and smeared the muffler cement about 1/4" think on each side of the gasket. Tightened everything up and then smeared some of the excess around the flat edge surfaces to make it easier to see any leaks. I let it dry overnight before starting it and it worked perfectly...no leaks! That was a week ago, I'll post an update if/when it starts leaking again.

Jrgunn5150 · Sep 26, 2016

Nicely done!

superdave · Oct 3, 2016

superdave said:
Had that issue with mine after putting on my headers. Another new gasket with Permatex ultra copper max temp silicone (or something like that) fixed it right up. I just think it's damn near impossible to get that surface flat.

Why did I have to post this crap? I was changing my oil yesterday and heard the leak again when I cranked it back up. I guess I'll be doing that job again. I have some muffler cement that I'll try as a sealant since it worked for the above poster.

'97 ECSB 5.7 Vortec exhaust flange leak

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