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View Full Version : blue smoke on start-up (boxer engine)



w261w261
10-02-2007, 06:52 PM
Not 3G, but we got the best techs around, so I thought I would post.

I also own a '92 Sub SVX, the one with the funny windows. It has a boxer 6 with about 80k on it, and I'm starting to get a big cloud of blue smoke in the mornings when I start it up - big enough to be embarrassing. No significant oil usage, and no smoke after the first cloud until after it's sat for several hours.
With a regular engine, that says "valve guides," but on the boxer the guides are horizontal. The Subaru dealer says maybe a stuck PCV valve, but on this motor it's hard to get to and I wonder about the diagnosis anyway.

Any suggestions?

shepherd79
10-03-2007, 03:17 AM
it is possible that PCV valve is cloged, but most likely it is your valve seals.

2oodoor
10-03-2007, 03:26 AM
I dont know the geography of specifics on that engine but you may want to check the oil cooler and plumbing as well as the pvc plumbing . What kind of oil does it use? See if you can see any signs of seepage around the cylinders (external) and tubes.
Does it do it even after its warmed up , like at an errand stop and then back on the road?

w261w261
10-03-2007, 05:07 AM
Does it do it even after its warmed up , like at an errand stop and then back on the road?

No seepage, and it doesn't do it after a brief stop, only if its been sitting.

2oodoor
10-03-2007, 05:14 AM
No seepage, and it doesn't do it after a brief stop, only if its been sitting.
Ok, im not an expert on Subu but I can try and help. I will look up some things on Mitchell later today.
Cold start enrichment- I am not sure how that one works on the Subu, but additives they are putting in the gas now are ripping these kind of things up.
Also, what kind of oil filter? did you change brands.. some have bogus check valves in them.

bubba g
10-03-2007, 05:30 AM
My VW did something similar when the rings were getting worn. On a horizontally opposed engine the excess cylinder oil can seep past the rings into the combustion chamber due to their design. It will not be enough to smoke all the time but just at start up.

2oodoor
10-03-2007, 05:57 AM
ok if you need any diagrams I can fax them. /The pvc is under the intake.
Therre are a lot of TSB on that car stating that you have to use premium fuel in the turbo car, and otherwise all are particular about fuel in general. It will not act well at all with Alcohol blends they are sneaking on us.
They are known for injector failures because of fuel additives particulaly seasonal changes in fuel supplies.
I havent found an oil path diagram yet but still looking.

w261w261
10-03-2007, 06:40 AM
thanks for all your help guys. the car is a non-turbo btw. 3+ L flat 6.

Blkblurr
10-03-2007, 10:31 AM
Valve guide seals is what causes this on most engines.

2oodoor
10-03-2007, 11:03 AM
Valve guide seals is what causes this on most engines.

however true that it is, this is pancake six so gravity is different. There may be some other seal though that is leaking by via gravity.
He says no real oil loss, so the smoke could be gas or both oil and gas if it is injector washing the cyl.

w261w261
10-03-2007, 05:46 PM
I checked the oil level this afternoon, and it shows 1/4 qt overfill. Maybe that's enough in this engine to run down a cylinder wall and past the rings. Will drain out some when my son gets back and see what happens.