OK, a 1999 SOHC EJ25 81K .......This motor has a puff of blue smoke after a warm start. (Vehicle previously run and then shut off for a short duration). No smoke while running/driving and no smoke from a COLD start. (Just that damn piston slap)!!

 

New mobil one 15W50/correct level. Runs/drives fine. No oil usage to speak of. Have noticed a blackened tailpipe inside surface though.

 

Valve seals already! Can these be replaced with heads on car/engine in car?

 

Thanks you New gen gods!

 

Todd

That sounds odd. I'm inclined to think valve seals except you say there's no smoke on cold starts. Normally after sitting for 8 + hours more oil would leak pass bad seals (more time = more oil) and burn off on a cold start. Maybe you have 1 valve that's not seated quite right and doesn't show up until after warm up. Do a cold then hot compression test check if one cyl maybe off too much. There'll be differences between the cold and hot test but they should be fairly uniform say cold you get 150 hot 140 except one cyl is 130.

you'd have an issue that is probably valve seating related. Maybe others will have better ideas but that's where I'd start. Good luck

That sounds odd. I'm inclined to think valve seals except you say there's no smoke on cold starts. Normally after sitting for 8 + hours more oil would leak pass bad seals (more time = more oil) and burn off on a cold start.

No matter how good and "multi-vis" the oil, it's thinner when hot, and will get past small openings more readily than when cold and more viscous.

 

 

Maybe you have 1 valve that's not seated quite right and doesn't show up until after warm up.[...]

Perhaps I'm missing your point, but valve seating shouldn't relate to oil getting into a cylinder. Valves in an engine that isn't running normally are at various degrees of being open -- however that's to either intake or exhaust manifold, not sources of oil unless something is really wrong.

Long shot here, but when was the last time the PCV valve was changed (odds are it hasnt been changed). Thats the biggest cause for subaru oil burning. I would rule out stem seals right now.

 

How much oil are you actually using? If your burning it, your using it, and it should be dropping between oil changes.

 

It takes very little oil to make lots of blue smoke.

 

If you are still worried about it, a compression test is next on the agenda, but i'm guessing its the pcv valve.

 

nipper

Your right I'm perplexed and grabbing at some other explaination. Besides doing a compression test never hurt anything and just may show something. My second point the longer an engine with bad vavle seals sits after running at operating temp the more time the hot thin oil has to leak by the seals. After that it sits in the combustion chamber (valves closed) or in the cyl(s) valve(s) opened until the engine is started again. Therefore smoke from bad seals should be worst with a cold engine than hot. I don't understand in this case why it's not happening. Why would the smoke happen with the hot engine but not cold??

As the engine cools down, a cylinder that is sealed, creats a vacum.

 

This is just a really long shot theory understand...

 

 

That is when the oil may be sucked in, but I still think the PCV valve should be changed first before we really start looking for a problem that may not exist.

 

 

 

nipper

And use a subaru PCV valve from the dealership, the aftermarket ones have a reputation for poor quality.

This forum is great!!! (If you gen 1 advise......always feel free to ask me, so I can return favors)!

 

I will check the PVC valve today.

 

I'll update.

 

Todd

The interesting thing is that the PCV valve I think is the same as your Gen 1's....

 

One of those weird parts that hasn't really changed.... ever.

 

GD

See subarus are almost human. Us humans carry over some parts from way back when, so do subarus

 

 

nipper

Affirmative - listings I have show the same part up till 2002 for basically every Subaru.

 

GD

Check those PVC hoses also, the 2.5 I rebuilt in Nov, had huge amount of oil sludge in them blocking off the hose. I ran a small bottle brush through them to clean them out. Oh Yea, the PVC valve was stuck shut like these guys are telling you to check for.

Well, it has a VERY weak suction when the car is running. The hoses are somewhat blocked too. I'm looking through my piles of subaru stuff, I know I have one!

 

Ya know, it's so frustrating to have tons of Subaru crap, but I can NEVER lay my hands on something I know I have, when I want it! Anyone else have that problem?? I can SEE that PVC valve in my head...I think it walked off!

 

Todd

OK changed the PCV valve and it only has a very short tube going to the crankcase....all the tubing was OK. Still get that puff of smoke.

 

Now I noticed that after a drive, if I sit in the driveway and rev to 2000 rpms or so, it smokes too! Hmm??? Not a ton, but enough to see. I'm doing a compression check next.

 

Car went to Subaru today for headgasket check and it's OK on that front.

 

FYI The car runs 15W50 Mobil 1

 

I'm not likeing these 2.5s already!! GIMMEE my 2.2s!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

Todd