Failing AOS - w/Video?

Last weekend on the track, after a rather intense 25 min session, upon startup for the next session I had a James Bond style cloud of white smoke that cleared up after a minute or so. Immediate thought was that I overwhelmed the AOS on the previous session. No other symptoms since. I'd been meaning to test my existing AOS (replaced 4 years ago) so finally did this morning. I'm pulling over 8 in/H2O - seems like my AOS is starting to fail. What do the experts say? Continue to roll with it or bite the bullet and get started with replacement? Next track session is in a month. Here's a video so you can see the values from the Pyle Digital Manometer.

IF you decide to replace the AOS ,read some recent threads about defective ,new AOS units. There seems to be some q.c. and materials defects.

I would say replace it and prepare for the pain if you diy. See more info here http://www.callasrennsport.com/porsc...eparators-101/

What vacuum/low pressure does a healthy engine/AOS pull? I've never measured vacuum/pressure with a healthy or sick AOS. Did you take a cool down lap and then in the pits let the engine idle a couple of minutes? If not you could have loaded up the intake with oil and then the car sits and the engine hot soaks to beat the band and this oil in the intake runs down into the engine and smoke is what you get. If the smoking stays away upon cold or hot starts for a while maybe you just did overwhelm the AOS. Not hard to do. Even street driviing can do it. You have to be prepared though the next session the AOS lets go and the car is undrivable. Tough call. Hope the smoking was just a freak event and there are more miles plenty more miles in the current AOS but have some fear, well, anxiety at any rate, the thing is not long for this world and have to deal with a bad AOS when it goes completely bad on its schedule. Or replace the AOS preemptively.

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Thanks guys. Love it. "prepare for the pain". On a related note, I did see an unusually high amount of oil on the underside of the AOS. So much that it actually created a drip or two on the ground this week. Will likely get moving with a replacement. If I do it, will throw in a coolant expansion tank, coolant flush and may try an engine drop to test the clearance on the new lift. Or maybe I'll just write a check and lose some enthusiast street cred

Any oil leak on or around the AOS is already enough reason to replace it.

Actually removing the coolant tank will help AOS removal a bit and no need to remove the engine. Just lower it to the max. The oil leak could also be from the o-rings on the AOS corrugated hoses so its best to replace those too. Coolant tank + AOS on a MkII = max pain

From the link given by Ahsai to answer the question from Mcaster: "On BMW’s and Porsche’s the engine crankcase vacuum is normally around 5 inches) of water. When oil separators fail the crankcase vacuum can rise to the 8-12 range and even higher, depending on the extent of the failure... When the oil separator starts to fail on Boxster’s (986 & 987) you generally start to see a substantial amount of smoke from the exhaust tailpipe... When the oil separator fails on 996-997s, it usually does NOT create the same exhaust tailpipe smoke as a Boxster. It is almost like being a silent killer (and a costly surprise)."

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Someone was selling the Motorsports AOS unit in the classifieds... is that worth it, in terms of a "one and done" fix? Assuming one could get it for say, $600?

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I've read some other threads that said yes. But sounds like getting that sucker to fit is quite a challenge and may require a custom bracket.

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Quick update on my symptoms and the before and after... The video clearly showed 8 in/H2O as the before and with a new AOS I'm happy to report a reading of 3.9 - 3.97 in/H2O via the digital manometer. For those who suspect a failing AOS: I only had smoke on startup once after a 25 min track session I had a very mild rough idle I never had a CEL, no pending codes from the durametric No other symptoms The failed AOS (OE Porsche) was less than 4 years old My failed AOS was mostly silent in its symptoms - not sure it was a "killer" but the symptoms were subtle until the track smoke out.

Well done. Mine measured ~10" water out of the box and I had to replace it again so I did the job twice. These AOS are unbelievably fragile. So how did you get the rear AOS bolt?

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I called in reinforcements! The rear bolt was a 13mm (which didn't really fit) and was impossible to remove without partially dropping the motor or transmission. No wonder I struggled so much. The shop ended up replacing both with the correct 5mm hex bolts which should make it much easier when I do this next time. Was almost a full days labor due to the hacked rear bolt.

I am pretty sure you mean 5 mm socket head bolts. That is what mine had. Didn't help that the socket heads were full of oil and dirt so you couldn't get the tool in. I now understand why it seems to be SOP to drop the engine to do the AOS, and you can then also readily access all the hoses and o-rings to put the system back in 1st class condition.

^^ +1

Thankfully I found this thread, as I think I may have the same problem after a track day last week? After my first session, someone came up to me to let me know my car was smoking a little during the run. I kept an eye on it and after my second run I asked the guy behind me if he noticed any smoke and he said that he didn't see anything. As soon as I started my car for the third and final session, I had a huge cloud of smoke and immediately shut it off. Knowing I had to drive 3 hours back home, I left it off until time to head home. Upon starting it, I had the cloud of smoke again and smoke coming from both exhaust pipes pretty heavily but got less and less. I went with two friends so I followed one, where the other car followed me on the way home. After about a mile my car no longer smoked, and I no longer babied it, accelerating hard, engine braking, and no more smoke on the three hours drive back. I originally thought I may have had a little too much oil in it that overflowed until I mentioned it to my friend at the shop and he sad it could possibly be the AOS, which he says is a huge pain to replace. From what I mentioned, does this seem like the AOS? I am assuming from what I am reading that I should no longer drive the car until this is replaced to prevent engine damage? If it is the AOS, any recommendations or do you just use a OEM part? Thanks in advance!

No need to guess about the AOS - just measure the vacuum as mentioned previously. Note problems with defective new OEM AOS units also mentioned. You may want to research 'baffles' for Track .Brey Krause and others.

It may not be the AOS...check it with the method I used and you'll know for sure. My other advice is to let the engine cool off a bit when coming off of the track. You can either extend your cool down laps, drive around the paddock, or simply let the car idle for several minutes after each session. Go a few minutes longer than you think. If I do this, then there is no blinding white smoke screen at start up. Mine, and many M96 powered cars I see on track, will smoke on startup if not properly allowed to "calm down" after each session. Normally I let the car idle until my adrenaline has subsided to acceptable levels.

Thank you for the advice!

Defective new AOS? Really? Just what I need to hear as I am getting ready to tackle it. Ugh, I don't want to do it twice!

2nd time is so much easier though! :P

I did an AX last year and after the first run, it was smoking like crazy and then slowly faded away. Upon each next start up, it smoked bad for a few minutes and lasted like that for about 3 months and then one day, nothing.. its been fine ever since.. weird..

I am running the Toyo Proxes R888's which are pretty sticky and can seem to make the problem worse because of the G's the car is pulling. I was also at Atlanta Motorsports Park which has a lot of elevation changes and is known to be hard on engines. Oh well, I guess I will have that vacuum test done to see if that is the issue? My shop recommended getting the Motorsport AOS and then quoted me $900 for labor... ouch..

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The Motorsports AOS is I recall more durable and thus less likely to fail under the rigors of tracking but its ability to remove oil vapor under the rigors of tracking may not be any better than that of the stock AOS. You might end up with an expensive AOS installed and yet the engine still emits the smoke at times. Another course could be an oil catch can. I would think the place for this would be in the line/hose from the AOS to the intake. This catch can would give the oil in the engine fumes one last chance to leave the fumes before reaching the intake. Not sure of the interior of the catch can. In some cases just arranging for the fumes to come in and leave with a sharp turn (or two) is sufficient to cause the oil vapor to leave the fumes and impact the walls of the can. Or perhaps some internally baffling to create a bit of a labyrinth to cause the fumes to change direction a few times to more effectively remove the oil vapor from the fumes. The catch can would have to be mounted securely. It would need to have a drain as it will fill up after some time and you don't want to risk liquid oil being fed to the engine at any time.

OTC 4525 makes all the difference for a DIY install

or the original by Mayhew https://www.amazon.com/Mayhew-28650-.../dp/B0000T4UI4

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Regarding defective new OEM AOS units.... Replacing a failed AOS on a 2006 Cayman S, I purchased a brand new, Porsche AOS unit. Installed it on my car only to see the oil fill line collapse immediately. It was clear the diaphragm valve was not closing inside the new AOS unit, so immediately removed it from the motor. I did a bench test of the new AOS (see drawing: sucking on the port marked by the red arrow which goes to the intake manifold, while simultaneously plugging off the other 3 ports marked by the blue arrows). You SHOULD be able to hear the diaphragm move internally, but my test indicated no movement of the diaphragm. I removed the approx. 3" round plastic cover from the diaphragm carefully and found that the diaphragm was not seated inside the perimeter ridge. I inspected the spring and all other parts, which seemed fine. I used a small amount of RTV sealant to seal the diaphragm to its perimeter seat, replaced & reinstalled the plastic cover and then repeated my 'sucky test!!!!' This time you could hear the diaphragm move internally. Re-installed it on the car and the oil line did not collapse....AOS now working perfectly. Defective new AOS cost me several hours of troubleshooting. Suggest 'sucky test' on any new AOS you may purchase prior to installation.