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Registered
2004 Forester XT
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372 Posts
Discussion Starter #1
Hey all,

I just bought a used STi TMIC and noticed that it has a thin oil residue on the inside. It's a little thicker in the red coupler from the turbo. Is this normal build-up from blow-by, etc. for a car that is a few years old? Or is this not normal... like this guy has a turbo leaking oil?

Anyway, can it be cleaned up by spraying some degreaser in there and flushed, or should I return it?
 

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Administrator
2007 Forester Sports XT 4EAT
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39,490 Posts
It's caused by routing the crankcase vapors back into the intake. It's not a good thing, since any dust that makes it thru the air filter will cling to the surfaces coated with oil. It can be reduced by installing an oil catch can or an AOS (Air Oil Separator). :wink:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 

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Premium Member
2008 FSXT 4EAT
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4,143 Posts
When I inspected my stock TMIC during my build, the inside was bone dry and didn't have a single trace of oil - that is good. I'd venture to say a thin film of oil on a TMIC that's a few years old is normal, but undesirable, and can be prevented with a catch-can, as mentioned above. :)
 

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Premium Member
2004 FSTI automatic
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2,643 Posts
I'm fairly sure you can clean up by flushing some warm water & gentle soap...
I plan on tearing things apart and swap/clean some hoses too since I have added my new AOS.

I have mucho blowby sludgies...
 

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Registered
MY09 XSn 2.0 Diesel 6MT
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967 Posts
As previous poster's have stated, it's the normal result of the crankcase oil vapours being routed into the air intake to help with emissions control. But not at all desirable, since the oil condenses out of the vapour as it cools in the intake, coating the pipes/turbo/IC. This coating builds up over time and impedes the airflow/heat transfer within the IC, effecting throttle response.

The only way I know to stop this happening is to disconnect the feed pipe from the crankcase. But that presents legal problems and makes a big mess in the engine bay/on the road.

Over the eons I've tried venting to atmosphere, breather filter, catch tank/vapour trap, and currently a Heath Robinson AOS. So the question is to the Forum, of all the current after-market options, which ones actually work :icon_question:


XTDude, remove the IC and reverse flush & drain;
1st with a solvent (Gunk), maybe more than once
2nd with hot soapy water
3rd with hot water
Don't poke anything into the IC to clean it, it breaks very easily.
 
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