968s sucking oil into engine somehow???

[piersman]

Originally Posted by Jake Raby

In my experience the smoke that is emitted from these engines when cornering IS NOT the fault of a scavenge pump. I see this condition routinely and have only had a scavenge pump replacement dove it in the instances where a scavenge pump has failed.

Hi Jake , thanks for your comments. You said the above before going on to explain the impact of a pump being seized by engine parts.

What is(are) the cause(s) of cornering smoke that you've found? Something on my car is causing the AOS to suck up and throw large amounts of oil into the engine when 'pressing on' , particularly if having just exited a left hander.

What oil do you recommend? The AOS is 3 months old.

Thanks

[Jake Raby]

Originally Posted by piersman

Hi Jake , thanks for your comments. You said the above before going on to explain the impact of a pump being seized by engine parts.

What is(are) the cause(s) of cornering smoke that you've found? Something on my car is causing the AOS to suck up and throw large amounts of oil into the engine when 'pressing on' , particularly if having just exited a left hander.

What oil do you recommend? The AOS is 3 months old.

Thanks

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.

[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

[kiyakubuke]

so I just had my car checked out by the dealer and by a local repair shop specializing in European cars. they both confirmed that it was indeed the AOS. the dealer quote has been blocked from my memory for my own sanity, the repair shop quoted me $700. another $375 to replace the spark plugs. I can only assume a BJ was included in that price. regardless, I opted to get the part from Pelican for $132.75 and a set of plugs for $36 and will fix it the weekend.
Next weekend, I will spend the $800 I saved doing it myself.

[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?