968s sucking oil into engine somehow???

[seningen]

Originally Posted by Jake Raby

Either you have a bad "New" AOS (which we see all the time when testing with a Manometer) or the valve stem seals are hardened and allowing oil past them.

This is what happens with the glorious engine oil and service intervals dictated by the factory.

Hardened stem seals allow oil to be sucked past the intake valves during heavy manifold vacuum. Oil that puddles in the cam covers from G force aggregation can also leak past exhaust stem seals and end up in the exhaust system.

Worn valve guides can have a similar impact as the excess movement in the valve impacts the ability of the stem seal to do its job.

Not to question the above which are all good suggestions/observations:

Could Ovality come into play here causing blow by which is overwhelming the AOS?

If so -- what is the easiest way to check?

Mike

[The Radium King]

I thought that - did a basic compression test. got equal values across all cyls so, unless all cyls are equally oval, then you are ok.

[Jake Raby]

Typically an engine with that much cylinder ovality would fouls plugs, log misfires and it would sound like a diesel.

[healthservices]

In my case it seemed a little crazy to install a third AOS valve. but it must have came from the crankcase, because the smoke and wet intake stopped as soon as I removed the tube to the intake from the AOS valve.

If it did return I would think rings or valve seals...

Valve seals because the crank case pressure is forcing the oil past the valve stem seals

[piersman]

Well I've just checked the pipe out of the top of the AOS and there's definitely oil residue in the pipes.

As expected, the car smoked for a few seconds as it cleared whatever oil had run into the engine from the last 'episode' last weekend, and now runs clear , and will stay clear now after a few starts until the next time.

The oil is definitely getting up through the AOS somehow, despite the AOS being a new one and the car NOT displaying any of the classic AOS problem symptoms.

I'm going to change the oil again. I put in Mobil 1 0W-40 when i changed it 3 weeks ago, and the oil that drained out the car at the time seemed very free flowing. So I'm going to try something stickier, like 10W-60 and see if that makes any difference.

[piersman]

Went and picked up some oil and gave the car 1 brief blast on the way home, barely touched 5k and the smoke started out the back.

So checked the oil levels before starting the change, the level was right at top of dipstick level indicator.

So I've drained the Mobil 1, which runs like water , without changing the filter and replaced it with Castrol 10W-60.

I managed to drain out 7.5L and I've put back in 7L to get the dipstick level just to the minimum indicator. Does this sound right?

Lets see what happens tomorrow when I take it out.

[Steve Tinker]

Thicker oil won't help your problem - it may reduce oil consumption if you have bad bore / ring / valve stem wear, but 10W60 is way above spec for these engines - especially in a cold climate like the UK.
Also running the engine oil level @ minimum has its own problems when it comes to hard cornering oil surge and aeration.
Bite the bullet and replace the AOS, thoroughly clean out oil resedue in the inlet plennum and see how that transpires. If the worst comes to the worst, a compression or leakdown check will give you some clues before tackling (expensive) cylinder head aux oil pump problems.....

[Jake Raby]

As I had stated this exact set of symptoms can mean other mechanical issues are present causing the problem..

It's pretty simple, the intake should be dry of oil inside. If it is not, then the hypothesis of the AOS could be correct. There is no such thing as am AOS being "overcome". The only way that oil can make it past the AOS is if the internal diaphragms/ membrane has failed.

A manometer is the proper tool to test an AOS. Look for oil in the intake and test using a manometer. If the intake is dry and the AOS tests good, then you have oil entering the combustion chamber or exhaust port and being burned.

You can even have a bad oil control ring causing the issue. This can happen in corners as G forces push more oil to that side of the engine and puts the oil control rings through a workout.

A bad oil ring can have perfect leak down and compression test numbers and can even have better results than he other cylinders. Why? Because the extra oil provides a better ring seal for the compression rings.

This one can be tough to diagnose correctly. I see 2-3 of them per year.

[piersman]

Does anyone have a picture or diagram of the internals of the AOS , I'd like to know what's in there.

If I end up buying another AOS I'll strip this one down to see what's going on inside, but it would be good to know what should be in there and how it's supposed to work.

Cheers.

[Frank A]

I have a 2000 Boxster S that smoked just like yours when I bought it.
If I took a spirited left hand turn the oil smoke was amazing.
I changes the AOS, cleaned the intakes, and still clouds of oil.
While I was changing my IMSB I noticed my pass side oil pump was installed wrong ( Keyed to 2-6 not 1-3) so it was not evacuating the head of oil.
My motor has over 120,000 miles so I'm sure the valve guides are hard and leak, but from the time I keyed the pump proper no more clouds of smoke.

Good luck

[Jake Raby]

Yes, a backward installed scavenge pump will certainly cause this.

[healthservices]

Originally Posted by piersman

Does anyone have a picture or diagram of the internals of the AOS , I'd like to know what's in there.

If I end up buying another AOS I'll strip this one down to see what's going on inside, but it would be good to know what should be in there and how it's supposed to work.

Cheers.

I think someone cut one open, basically just a baffle. Maybe when I have time I'll cut one of the ones I have open....



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[kiyakubuke]

So my 2001 S is having identical issues. first noticed it at the track doing some 0-60 times. on the second run just as I hit 60 a big puff of smoke came out the exhaust. I thought I had blown the engine, but it ran fine. on the way home it smoked a little on hard acceleration (getting on the interstate) but ran perfectly. of course I took it really easy all the way home. noticed it did it the next day on startup but not on the following days. seems now that if I drive it a little hard, it may not smoke then, but on startup the next day it will. had it do it once more on the interstate passing some cars.

so, of course I have been researching this and talking to some folks. I have a friend that has had several Boxsters and talked to some guys at the Porsche driving school at Barber Motorsports Park in Birmingham. most of them were like, "yeah, they do that." most of them have upgraded their AOS with the "High Performance" version to prevent this issue on the track.
Still, "some dudes at the track" are not, in my mind, the final word. I plan to have the car checked out completely, but at least I am not in a panic anymore....for now.

[kiyakubuke]

I think mine is falling into the AOS failure category
Replace the Air/Oil Separator

[healthservices]

Eh... time is money and the amount of money they are charging is actually less than what the dealer and many independents charge for the same job.

And good for you for tackling it yourself!!!

[kiyakubuke]

Originally Posted by healthservices

Eh... time is money and the amount of money they are charging is actually less than what the dealer and many independents charge for the same job.

And good for you for tackling it yourself!!!

I could see the $700 for the AOS, if it was something I couldn't do myself. but $375 for changing out some spark plugs seems a bit much.

[healthservices]

If I remember correctly the middle one was a new AOS I replaced because I thought it was faulty. I should cut that one open to see if the membrane is damaged. Is there a way to apply vacuum to a AOS to check its integrity off of the motor?

[kiyakubuke]

Originally Posted by healthservices

If I remember correctly the middle one was a new AOS I replaced because I thought it was faulty. I should cut that one open to see if the membrane is damaged. Is there a way to apply vacuum to a AOS to check its integrity off of the motor?

not sure, but it seems that if there is oil build-up on the intake side of the AOS, that would be an indication.

so, did replacing it solve your issues, and what were your issues.

mine was basically heavy exhaust smoke on high revs under load and on startup after a heavy load incident, eventually some fouled plugs causing #5 and #6 cylinders to misfire.
I'll report back next week after I have replaced the AOS and plugs and tested.

[healthservices]

Replacing the AOS a second time did not help, my issues was assume to be the oil pump as the AOS still was puking out oil after replacement and with the intake hose disconnected the oil was still forcing its way pass the AOS out the hose and into a rag. For me swapping the scavenge pumps drastically reduce oil smoke. I replace the scavenge pump and that was that. I no longer have that car.

On your car, you should:

1. pull the throttle body and joint, clean the intake of oil with a rag or towel, reassemble but,
2. Put a plug in the intake where the AOS hose would go...
3. Put the open end of the AOS hose into a rag and into a catch can. Bring a fire extinguisher just in case. but nothing will happen
4. Run the car hard three times or until a cloud of smoke starts. no need to run car more than three hard times.
5. pull the engine cover, if...


If no smoke was made during the test, see if the AOS puked oil into the rag or catch can. If it did the AOS is bad again, oil is forcing its way thru the AOS, or you have bad enough blowby that is causing the oil to force its way out. Intake should be clean of oil since it did not smoke.


If it did smoke smoked during the test, make sure the oil did not puke out of the AOS tube into the rag and onto the exhaust. If it did not puke oil and there was a oil cloud, then the oil is from the rings or the valve stem seals

Jake should be able to correct me about my assumptions from these outcomes or give more input..