Hi Guys,
Scratching my head a bit on this one. '86 951 has elevated oil consumption (1qt/4-600 miles) and smokes only in one scenario:
If I'm coasting down a hill or engine braking (deep vacuum) and tip in the throttle it'll puff a bit of smoke.

Other than that the car pulls very well and doesn't have any other related symptoms. Intake piping and manifold are clean & oil free. I'm using 20w50 VR1.

I'm thinking it's either valve stem seals or maybe the turbo. Something is sucking oil in somewhere when the car is in vacuum and then spewing it out when I get on the throttle.

Has anyone ever ran into an issue like this? I was recommended to drive with the oil cap loose to rule out blow by which I'll try tonight.


Thanks

 

How many miles are on it ?

Has it ever been overhauled ?

Sounds to me like an either / or situation of stem seals or piston rings causing the blow by. Common with high mileage or abused turbo engines. If the car has had a lot of boost pressure added OVER the stock pressure, ring cracking may occur.

If your turbo is the cause of the oil consumption, you will see it gathering in places other than the inside of the tailpipe...... or the garage door, wall behind the car, etc. It will be putting oil everywhere, especially on the intake side.

 

130k Miles. It has not been overhauled to my knowledge.
I got a friend to drive it while I followed him today and it would really only smoke in the above mentioned scenario and just for a split second.

I'm leaning towards valve stem seals

 

Could also be a slight oil leak from the turbocharger. How do your spark plugs look?

 

I was wondering about that. Maybe the oil is pooling up during vacuum and then getting shot out the exhaust when I touch the gas? Plugs:

 

If you do not have any signs of dark smoke when you start the car and when it's idling, it's probably not rings or valves. Do a compression and leak down test to confirm, but I think it's from your turbo.

 

I'm going to try and do the valve stem seals this wkd with the head on. If that doesn't do it, i'll pull the turbo and visually inspect the bearings and the thrust plate and see if there is significant wear/oil on the hot side housing.

 

Got a little work done tonight:

Plugs (old but clean...I doubt I have an oil control ring issue)



Compression #s after the car has been sitting 9ish hours (throttle plate open)


Starting to think turbo more and more. I'll do a warm compression test if I feel like burning my fingers later on.

 

Compression looks really good. Can't imagine you have any issues with head or rings. When you look at the turbo, also check the o-rings for the oil inlet line and return in the mount.

 

Found my culprit:


enlarged turbine bushing bore (notice the ovaled oil feed hole)



Looks like the oil was going past the piston ring seals of the turbine side:



time for a new churbo