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Discussion Starter · #1 ·
So this past weekend my AOS failed again. Porsche is trying to uncover why, but so far they have not found a solution. This got me researching, which raised two questions I'd like to put out to the masses, so that I might learn from your experiences.

1. To those of you who have suffered multiple AOS failures: did you find out why, or did you/Porsche just fix it and move on?

2. To those of you who upgraded to the motorsport AOS: did you continue to experience AOS failure, or did the upgraded part make a difference?


Thanks to all who participate! Cheers!

Deutsch
 

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To add a datapoint, I had a 36k old AOS on my 08 CS. I switched to an IPD plenum+gt3 throttle, which removes/blocks one of the intake to AOS vacuum lines. No issues after a few months of hard autocross running. For testing I switched back to the stock plenum for one event, and within 2 runs had an AOS diaphragm failure. I think there is some merit to blocking one of the intake to AOS vacuum lines to help isolate it from severe vacuum fluctuations caused by rapid rpm/throttle changes.
 

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To add a datapoint, I had a 36k old AOS on my 08 CS. I switched to an IPD plenum+gt3 throttle, which removes/blocks one of the intake to AOS vacuum lines. No issues after a few months of hard autocross running. For testing I switched back to the stock plenum for one event, and within 2 runs had an AOS diaphragm failure. I think there is some merit to blocking one of the intake to AOS vacuum lines to help isolate it from severe vacuum fluctuations caused by rapid rpm/throttle changes.
Off topic: what series are you gonna run this year?
 

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Discussion Starter · #4 ·
Not sure if the issues are related, but just found out that on top of the AOS failure, I have coolant in cylinder 2. Tearing down the motor now to see if its a head gasket, or a cracked block. Its odd that the car never threw a code for misfire, or for low coolant...hopefully that's an indication it was caught early on and there isn't extensive damage...although, a new motor would be nice.
 

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Not sure if the issues are related, but just found out that on top of the AOS failure, I have coolant in cylinder 2. Tearing down the motor now to see if its a head gasket, or a cracked block. Its odd that the car never threw a code for misfire, or for low coolant...hopefully that's an indication it was caught early on and there isn't extensive damage...although, a new motor would be nice.
Hoping it isn't too bad for ya man.
 
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Discussion Starter · #9 ·
From Pelican Parts: " The engine air-oil separator is an emissions device located on the top right rear corner of the engine. The separator is responsible for collecting residual gases and vapors contained inside the crankcase and funneling them back into the intake manifold where they can be burned in the combustion chamber. This reduces the overall emissions of the engine.

When the separator fails, you will begin to see a large increase in the overall vacuum in the engine crankcase. In the most extreme cases, the air-oil separator fails to separate the oil from the air, and oil is then sucked into the intake manifold. Oil in the intake system is not healthy for the engine and it can foul spark plugs and destroy catalytic converters at the very least. The failure of the air-oil separator is often (but not always) accompanied by huge amounts of white smoke exiting the vehicle's exhaust and a generally poor running engine. You may experience a check engine light (CEL) as the oil being drawn into the intake can affect the mixture level. The oil cap may be very difficult to remove when the engine is running due to high vacuum levels. In addition, you may hear a high-pitched squeal from the engine when it's running: this is caused by air being sucked in past the crankcase seal due to the extreme vacuum inside the case."
 

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From Pelican Parts: " The engine air-oil separator is an emissions device located on the top right rear corner of the engine. The separator is responsible for collecting residual gases and vapors contained inside the crankcase and funneling them back into the intake manifold where they can be burned in the combustion chamber. This reduces the overall emissions of the engine.

When the separator fails, you will begin to see a large increase in the overall vacuum in the engine crankcase. In the most extreme cases, the air-oil separator fails to separate the oil from the air, and oil is then sucked into the intake manifold. Oil in the intake system is not healthy for the engine and it can foul spark plugs and destroy catalytic converters at the very least. The failure of the air-oil separator is often (but not always) accompanied by huge amounts of white smoke exiting the vehicle's exhaust and a generally poor running engine. You may experience a check engine light (CEL) as the oil being drawn into the intake can affect the mixture level. The oil cap may be very difficult to remove when the engine is running due to high vacuum levels. In addition, you may hear a high-pitched squeal from the engine when it's running: this is caused by air being sucked in past the crankcase seal due to the extreme vacuum inside the case."
Thank you!
 

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I replaced my AOS with the 987 Motorsport version since I was going to drive the car on the track. So far so good after 4 years. One wrinkle with installing the larger AOS on the 2.7L engine is that the ECU needed a flash (Softronics) to keep the CEL off because the stock 2.7L ECU thinks there is a vacuum leak. 3.4 L ECU software seems to handle the 987 Motorsport AOS without CEL.

Rob
 

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My AOS failed during my second year of DE events (9 events). I opted for the motor sports AOS via the local dealer, three years later and many additional DE events with no issues to report.

The failure occurred while I was in the yellow run group riding on PS2 tires ... At the time I had bilstien coil overs, tarret sway bars and a "track" alignment.

The tech who worked on my 2006 Cayman S was honest and explained every model has a weak point and when heavy tracking is involved these become exposed and become more prone to failure. Moving forward I took the proactive approach and added a Mantis gen 2 deep sump, 3rd rad, LN oil change package, low temp thermostat and switched to Motul oil. 3 years later no issues to report.

My tech explained
 

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Off topic: what series are you gonna run this year?
Mainly autocross and pro solo still with the '09 pdk. Will start running track events with this one and possibly one lap this year if resources line up.

Back on topic, after I reinstalled the ipd plenum, and blocked one AOS vacuum line, no more issues in 18mo. of hard use, with another oem AOS. There are some threads on Boxster forums talking about restricting flow in those lines with washers for a similar effect. While you should have some vacuum available to the crankcase venting, the oem configuration seems to be under too much stress at high revs and g forces.
 

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I replaced my AOS last summer after doing the DE at Laguna Seca and a total of 4 DEs on a 6 yr old AOS. If you've ever seen the internals of an AOS, the membrane that does the separating looks pretty thin. Doesn't appear it would take much to pierce it and at that pt vacuum would rip it good.

I've purchased the IPD / GT3 TB from Suncoast when they had their Christmas sale but haven't put them on yet. If you block the part that goes into the intake, how would you know if an AOS fails? Isn't that where the tell tale signs of oil getting into your intake system comes from that's letting you know it's failing? Haven't you just eliminated that avenue?

BTW... the AOS on my LE is still original and working fine - 7 yrs old, 42K mi, 0 DEs.
 

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I replaced my AOS last summer after doing the DE at Laguna Seca and a total of 4 DEs on a 6 yr old AOS. If you've ever seen the internals of an AOS, the membrane that does the separating looks pretty thin. Doesn't appear it would take much to pierce it and at that pt vacuum would rip it good.

I've purchased the IPD / GT3 TB from Suncoast when they had their Christmas sale but haven't put them on yet. If you block the part that goes into the intake, how would you know if an AOS fails? Isn't that where the tell tale signs of oil getting into your intake system comes from that's letting you know it's failing? Haven't you just eliminated that avenue?

BTW... the AOS on my LE is still original and working fine - 7 yrs old, 42K mi, 0 DEs.
Because of the way the plenum is designed there is only one line going into it from the AOS vice two to the stock plenum. If you had a failure it will still dump oil in the intake tract.
 
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Discussion Starter · #17 ·
Is blocking one hose to the AOS part of the install instructions for the upgraded plenum?

Thanks to you all for the information, this has been a real education.
 

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Discussion Starter · #18 ·
Porsche called to inform me that my block is cracked along the cylinder wall. I hope a new motor prolongs the life for an additional 90K miles.
 

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Are they going to replace it???
 

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OUCH... I hesitate to redirect the thread to specifically AOS.
Looks like it is a plausible DIY, but any info on what dealers charge for the replacement?
 
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