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Reported or suspected cause
intermix
Reported cause
No successful repair reported for this finding.
1
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Read evidence and context
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Discussions that report identifying a cause
1
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Reported cause
The other issue is intermix, which is when the plastic parts start to crack and since the oem AOS runs both oil and coolant thru it, the crack can result in intermix, which you don't want to happen.
Leading evidence: 'intermix' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'intermix' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Replace aos(' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Discussions that performed work without a confirmed outcome
1
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Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
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Performed · outcome unconfirmed
Most people just test the AOS when running hot at idles......But the reality is they can spike up to a real high vacuum and suck up some oil, then go back to specs in 5-10-20 seconds...This is when they are in first stage of failure or " Stage 1 "...The AOS needs to be tested "dynamically"..
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
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Performed · outcome unconfirmed · Original poster
They told me it tested withing spec and did not need replacing at that time.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
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Suggestion · Original poster
In the spring I asked my shop to replace the AOS( to my knowledge its never been done)..
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Suggestion · Original poster
The spark plugs were replaced becasue they were fouled with burnt up oil, I have owned the car for 4 years now and I would estimate the oil consumption is around a quart every 800 miles.
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Suggestion
It's just that the oem AOS is unable to process oil and oil will get into the cylinders if you are running the oil at full, if you are parking the car on a hill or if you are aggressively driving the car.
Discussions that performed work without a confirmed outcome
1
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Performed · outcome unconfirmed
Most people just test the AOS when running hot at idles......But the reality is they can spike up to a real high vacuum and suck up some oil, then go back to specs in 5-10-20 seconds...This is when they are in first stage of failure or " Stage 1 "...The AOS needs to be tested "dynamically"..
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
Most people just test the AOS when running hot at idles......But the reality is they can spike up to a real high vacuum and suck up some oil, then go back to specs in 5-10-20 seconds...This is when they are in first stage of failure or " Stage 1 "...The AOS needs to be tested "dynamically"..
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
Yes I agree Glenn covered just about everything....start by testing the AOS again this time starting with engine OFF then starting to see if the AOS spikes to high vaccum on start-ups...
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
intermix
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
Read evidence and context
Discussions that report identifying a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Reported cause
The other issue is intermix, which is when the plastic parts start to crack and since the oem AOS runs both oil and coolant thru it, the crack can result in intermix, which you don't want to happen.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
4 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261027T000231Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
In the spring I asked my shop to replace the AOS( to my knowledge its never been done).. They told me it tested withing spec and did not need replacing at that time. The spark plugs were replaced becasue they were fouled with burnt up oil, I have owned the car for 4 years now and I would estimate the oil consumption is around a quart every 800 miles. From the spring to mid summer the car burned almost no oil that I could tell - driven around 800 miles. Never observed any smoke during start up (occasional during the rest of owneship period). I also had it borescoped in the spring and from the pictures it was determined to be a non-issue. I did post the photos here and consesus was the same. The last 500 miles ore so the oil consumption resumed, with smoke on start up most of the time. I don't see any smoke after it's running and I don't hear any rough running. There is a fan somewhere that I can hear kick on when i'm stopped at a light. I don't remeber hearing it at the beging of the year when oil consumtion was low but have heard it randomly throuout my ownership period. The oil pressure gauge is also reading a little high. During my ownership period I have never had a dash light come on and I have put about 9000 miles on it. It's stored Nov-March. So I guess my question is does the performance of an old AOS flucuate? Does a failing AOS affect oil pressure? What is the fan I can hear kick on when I'm stopped in traffic (AOS related or something else)? If the bores aren't scored and the AOS is fine how else can oil be getting in/buring up?
First thing I would do for your own piece of mind is to find
@Porschetech3
thread on the UAOS. In the thread is a procedure that you could do at home with a manometer and a few parts that you can buy on Amazon to test you AOS. I'll attach a picture of mine.
The second thing is to understand that the AOS can fail in many ways.
One failure has nothing to do with it cracking or breaking. It's just that the oem AOS is unable to process oil and oil will get into the cylinders if you are running the oil at full, if you are parking the car on a hill or if you are aggressively driving the car. Just a byproduct of the inefficient design of the oem AOS. The result is more oil consumption and smoking out of the exhaust at startup or under hard acceleration or coming out of a turn. So Porsche came up with a bandaid solution, which was to run the oil level a half a quart under full. Its suboptimal for many reasons.
The other AOS failure is when something on the AOS breaks or cracks, such as the diaphram, pipe, tube, etc. This type of failure is a bigger issue. When the diaphram breaks, oil will be sucked into the cylinders which not only smokes alot, but can result in hydralock which is when the pressure build up from the high qantities of oil and ignition in the cylinders resulting in the cylinders cracking. The other issue is intermix, which is when the plastic parts start to crack and since the oem AOS runs both oil and coolant thru it, the crack can result in intermix, which you don't want to happen.
The only solution to the failures is to put a better engineered AOS on your 996 that can process the oil more effectively at full and even above full by 1 quart, which can easily handle hills turns and heavy acceleration. In addition, one that doesn't dump oil in the cylinders but instead, drains it back to the sump. And lastly, one that eliminates the need for water coolant to flow thru it and therefore eliminate the risk of intermix.
This is the UAOS Track. Regardless what your indy says, besides upgrading your IMSB, RMS and replacing your water pump, I would replace your oem AOS with the UAOS Track. It's the Swiss army knife of aftermarket parts. It fixes alot of silly issues. Not to mention, you can improve your oil pressure stability because you will be able to run 1 qt extra oil over full, keeping your M96 happy with plenty of oil.
Best of luck with your next steps.
manometer
Yes I agree Glenn covered just about everything....start by testing the AOS again this time starting with engine OFF then starting to see if the AOS spikes to high vaccum on start-ups...
Most people just test the AOS when running hot at idles......But the reality is they can spike up to a real high vacuum and suck up some oil, then go back to specs in 5-10-20 seconds...This is when they are in first stage of failure or " Stage 1 "...The AOS needs to be tested "dynamically"..
The problem with factory AOS design has been overlooked for 2 decades with only full near catastrophic or catastrophic failures did anyone look at it... Then they just replaced with the same thing..
Yesterday, I did what Porschetech3 recommended and realized that my manometer needed to be set to capture the MIN value to record the maximum vacuum because it was a negative value. Just something to keep in mind.
Here�s what Porschetech3 posted yesterday about the same topic.
https://rennlist.com/forums/996-foru...l#post19691578
This is a source reference. Confirm exact model applicability in the original material.
