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Factory STi Manifolds, heat damage at flange (Solved: Casting Flaw)
Factory STi Manifolds, heat damage at flange (Solved: Casting Flaw)
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Old 08-30-19, 03:55 PM   #1
Bumblebeelotus
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Default Factory STi Manifolds, heat damage at flange (Solved: Casting Flaw)

Decided to pull my headers off and noticed the flange at Cyl 1/3 was showing some strange wear. Anyone have any insight?


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Old 08-30-19, 04:14 PM   #2
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Default Re: Factory STi Manifolds, heat damage at flange

I don't understand, what wear? I see carbon, a good seal on the fire rings and no signs of leaks.
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Old 08-30-19, 04:18 PM   #3
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Default Re: Factory STi Manifolds, heat damage at flange

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Originally Posted by killerbmotorsport View Post
I don't understand, what wear? I see carbon, a good seal on the fire rings and no signs of leaks.
If it looks normal, great! I was worried about the rusty/pitted portions on the right of each port.


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Old 08-30-19, 09:33 PM   #4
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Default Re: Factory STi Manifolds, heat damage at flange

Cast manifolds last pretty much forever, you're fine. Sometimes they will crack from quick changes in temperatures, say from a hot manifold getting cold water on it but other than that they almost never break, especially at the flange where it's thickest. Those "porous" spots look like carbon build, like killerb said.
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Old 08-30-19, 10:08 PM   #5
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Default Re: Factory STi Manifolds, heat damage at flange

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Originally Posted by UrdnotWrexSTi View Post
Cast manifolds last pretty much forever, you're fine. Sometimes they will crack from quick changes in temperatures, say from a hot manifold getting cold water on it but other than that they almost never break, especially at the flange where it's thickest. Those "porous" spots look like carbon build, like killerb said.
Interestingly they're actually holes, maybe .5mm deep... I'll clean it up tomorrow and get a better pic, but here's a closeup;



Cleaned it up a bit with sandpaper, could it be a casting defect? It's actually porous, and even seems to have warped the edge in places.


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Old 08-31-19, 03:26 AM   #6
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Default Re: Factory STi Manifolds, heat damage at flange

Now those pics are a bit more revealing. At first I thought it was just the 'normal' texture of carbon build-up, but now it seems like casting voids. Those were there when the car was assembled at the factory.

Anything that looks like it may be hanging or could break-off, I would hit it with a file or grinder to smooth it down a bit. This way no pieces will come off. Unless you're seeing something bad enough that looks like it could effect the integrity of the part, I would just touch it up and put it back together and be on my way. Going to a dealership and talking them into replacing this part (which they may argue is 'normal') is just not worth the effort IMO.
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Old 09-02-19, 09:36 AM   #7
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Default Re: Factory STi Manifolds, heat damage at flange

Quote:
Originally Posted by killerbmotorsport View Post
Now those pics are a bit more revealing. At first I thought it was just the 'normal' texture of carbon build-up, but now it seems like casting voids. Those were there when the car was assembled at the factory.

Anything that looks like it may be hanging or could break-off, I would hit it with a file or grinder to smooth it down a bit. This way no pieces will come off. Unless you're seeing something bad enough that looks like it could effect the integrity of the part, I would just touch it up and put it back together and be on my way. Going to a dealership and talking them into replacing this part (which they may argue is 'normal') is just not worth the effort IMO.
Appreciate it! Used some carbide bits to smooth it down, ended up rounding the edges on all of the ports.
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Old 09-03-19, 06:43 AM   #8
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Default Re: Factory STi Manifolds, heat damage at flange (Solved: Casting Flaw)

in the rust belts i have seen cast manifolds rust away or high heat crack them in half...super fun having a 3 piece manifold come off one side [email protected] could be comnbination of high moisture environment and exhaust gas making acidic moisture...is normal but shouldn't cause issues anytime soon!
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