Reinstalled stock cat pipe, exhaust leak mating to midpipe

[Siper2]

Posted on RS25.com:

Hey all.

Short version, I installed a Stromung HFC in April. I took it off today, however, as I've decided to do an engine swap and found a buyer for the HFC.

So I got the stock pipe put back on (pain in the butt!!!), but it seems I have a leak between the cat pipe and the midpipe. I did put a brand new donut from Subaru on the cat section, then bolted it up with the spring bolts. It seems that there's some play between the donut and the inner edges of the midpipe, though... plus the midpipe flange is bent a bit.

The bend happened prior to my buying it new. I'm not sure if straightening the slight bend would eliminate the leak, but I can definitely hear it when I step on the gas, and feel it with my hand. My thoughts:

- Some kind of exhaust epoxy to place on the space
- Perhaps the donut isn't big enough? If it's made for the stock pipe, which is under 2.25," then that's why there's some space in there...

Buy a donut for an STi?

Thanks guys.

Posted in one of the replies, but I checked the PN on the donut, it's the correct one: 44022AA062. I'm out of ideas.

EDIT 8/18/06: Issue resolved, see post #6!

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[JTJ 2.5]

If all else fails buy some high temp silicone (black tube) and apply liberally. Make sure to really push it into any openings. I would reccomend getting so rubber gloves the stuff is a pain in the butt to get off your hands. Give it 24 hours to fully cure and it should be gone.

[Siper2]

I originally was thinking that, but I've seen a few people say that it comes off. Who knows...

First effort's going to be to try to re-seat the spring bolts. If you check the RS25 thread, bisonjr (who lives about 45 minutes from me) has good suggestions. I actually bought the HFC from him, in fact.

-S2-

[Guerice]

The donut is made out of lead, give it a few days and it should mate better and stop the leak.

I had the same problem when i changed my cat section.

[Siper2]

Well, I tried reseating the spring bolts, bending, twisting and beating on the midpipe flange...

No bacon. Went to Meineke today, the estimate was free because.... they can't fix it. Not only is the forward midpipe flange deformed, but it's also cracked where it's welded to the flange.

THAT part ticks me off, because I was considering the turboback Stromung setup after I get my swap. Welds that crack after barely a year, though? Not appetizing.

So... I'm off to search for a donor RS catback. Just to hold me over 'til the swap. Which sucks.... because even the BroSpeed/SPT I had before was better than stock, in appearance. But some dude in Canada has mine, now.

Moral of the story, kiddies? If you go custom, have a pro do it. Not Meineke and Munro Muffler. Don't buy generic parts either. It's not worth your sanity.


As for the donut? It appears to have expanded some, but not enough to seal up and stop the noise. I think it's been long enough, doubt that it'll expand any more. Appears to be 1/8" (just eyeballing it) of a gap in there. Epoxy wouldn't work, moves too much, it'd just crack and flake off.

*sigh*

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[Siper2]

Originally Posted by Guerice

The donut is made out of lead, give it a few days and it should mate better and stop the leak.

I had the same problem when i changed my cat section.

I think you were right. But it took longer than a few days, and there's more to this story...

(Always is, with me. )

I brought the car to Meineke last week, they said they couldn't repair the flange and would have to replace the whole midpipe. I shook my head and politely left. Made an appointment at a small exhaust shop to check it out, but he couldn't get me in til next Wednesday.

For one last-ditch, pre-weekend effort, I drove the car to Midas after work yesterday.
The manager put the car up while the engine was running. I explained the whole thing, and he felt and listened for a leak at the midpipe/cat joint.

Nothing.

I was dumbfounded.

The noise was now coming from the cat/header joint!! Un-be-stinking-lievable!!! It was very clearly leaking from there, I could hear and feel the leak.

He gave me a handful of free gaskets, I thanked him heartily and drove home to let the car cool for ~45 minutes. Put it up on ramps and got to work. As it happens, the whole bolt for the upper end of the flange had fallen out. The nut apparently shook itself loose, I must not have tightened it enough or something. The nut was gone, but the bolt was hanging there, hadn't fallen off the car.

So I found another nut in my bag 'o' junk and tried to put the bolt back in. Talk about a tight space, holy cow. I had to remove my skidplate and drop the manifold down about two inches, to get the clearance. Plus hold the nut in place with an open-end 14mm wrench, and use a 9" extension on my socket for the bolt. Very delicate balancing act, this.

I did replace the gasket while I was at it. It's a metal one, but the only one of the bunch the guy gave me that was the same size, was black. Feels like a waxy, layered paper or something. Put that in there, buttoned it all up, started the car.

Blissful silence, except for my catback, which honestly sounds pretty good now that the HFC *and* leak are gone.

The drive to work this morning was interesting, though. Saw some smoke coming from my hood scoop, about four miles into the trip. The only thing I can think of? Headers are the hottest part of the exhaust, and maybe that's the wrong kind of gasket.

Didn't see any more smoke by the time I got here, but it still stinks a little. Should I be worried and rush to replace it with a metal gasket? Or just let it "burn off" for a day or so?

I'd be concerned, if it weren't that I got the gasket from Midas... an exhaust shop, after all....


So. Yeah. Peachy.

I'm still a bit miffed at the Stromung midpipe's forward flange, and how it bent like that. I think I figured that out, though. The first shop that put my catback together I think tossed my spring bolts and exhaust donut, because neither were there when I put the HFC on in April.

Stress crack, probably. Jerks...

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[Guerice]

Thank you for saying i was right

Yeah that bolt is a b*&ch to get at, but i can usually get there without taking the header off.

As for the gasket, if it doent catch on fire or leak, leave it there.

[Siper2]

That's what I'm concerned about, the fire thing. Kind of an issue, there.

Yeah I got the bolt in there last time, but I've no idea how. I think the engine was cooler and somehow I got my arms monkeyed up to a point I could get the bolt in place, is all I can figure.

Very easy to just drop the header down with a 6" extension and a deep-socket 14mm, so that's what I did.

-Chris

[TurbojonLS]

You could definitely be burning the gasket. I'd just check on it every day or so & see how its doing. And probably order a new one, just in case. Again, unless it sets itself on fire, I wouldn't worry much about it. There's also all the crap from your hands that's burning off - some of it can smoke, some just stinks.

[Siper2]

Yeah I thought of that, but on the other hand it wasn't smoking before I put that in there...

Still a bit stinky today on the ride home, not much. No smoke, at least wafting far enough up to see. I'll keep an eye on it.

-Chris