21 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHWhat's Leaking here..Do I have a RMS leak?
Reported or suspected cause
air oil separator
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
Read evidence and context
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 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.
Leading evidence: 'air oil separator' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'air oil separator' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Replace air oil separator' (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.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
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 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
Whether one of these possibilities is the cause is a job for you to eliminate each and every one.
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
The AOS can be changed with the engine in the car, but what a PITA.
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 suspect a cause
1
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Suspected cause
That high up about all it can be is oil from breather line and if that overloaded AOS is suspect #1.
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 suspect 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.
Suspected cause
I've had similar leaks on two occasions that turned out to be spark plug tubes and one (I think...
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Suggestion
My only experience with my 986 is learning how to recognize likely AOS failure signs then upon recognizing AOS failure likely speed dialing tow truck service to arrange to get car to dealer then paying the dealer service department to replace the failing AOS.
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Suggestion
Thus you could consider washing the engine -- I use Gunk and spray it on a warm (not hot!) engine, let it sit, then rinse with if I can get it warm to hot water.
Outcome qualification: Negation, uncertainty or missing explicit repair resolution overrides the raw extraction signal.
Coverage and how to read this overview
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.
21 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 · 1 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T161109Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
If you can't figure it out, get a pro to look at it. By the time oil gets down there, it's not always obvious where it came from. I've had similar leaks on two occasions that turned out to be spark plug tubes and one (I think... memory is foggy) that turned out to be the AOS. In any case, the minor possibilities vastly outnumber the major ones.
Is the breather line the larger bore hose connecting to the plenum just downstream of the throttle?
That's the thing I hate about the parts diagrams, they rarely show both sides of the line, so you'll have a vacuum line going from one part to nothing but a hose clamp. Great!
AOS can be done from rear of car or tranny side - with a tip, not sure which is easier. I did mine from the rear of the car and I cant see how the tranny would make a differance. It was a PITA to do, but not expensive and rather easy with the exception of the clamp (replace it with a screw type) and lining it up (stupid design, I thought it went into the hole further)
Can't answer question regarding Tip and engine drop for AOS replacement. I simply do not know if engine drop required for any 996 model/transmission combo.
I have no experience with 996 AOS.
My only experience with my 986 is learning how to recognize likely AOS failure signs then upon recognizing AOS failure likely speed dialing tow truck service to arrange to get car to dealer then paying the dealer service department to replace the failing AOS. I've done this two times now, in just over 226K miles of driving.
Sincerely,
Macster.
Hard to tell but the breather line going into the throttle body has a "O-Ring" on it and it is cheap change to test. Here is a link to picture with the line off and you can see the ring if you look close (first picture on right "click to enlarge".
http://www.webbspot.com/porsche/html/crank_vent.html
The AOS can be changed with the engine in the car, but what a PITA. I think the estimated time is 10-12 hours. You have to remove most of the intake to get at it, and thien it is still difficult . Almost easier to drop the engine. A good mech can drop the engine and reinstall in in about 8 hrs. Once the engine is down the AOS is a 15 minute job.
Oh.. and no white smoke from my exhaust... could it still be AOS? And when I open the oil cap while idling, the idle does drop and roughens... then smoothes out again. But the idle does not die. When I put my hand over it, I can feel the vacuum. I am going to take the air intake off to get a better view of the oil leaks.
Not all AOS failure modes produce oil smoke at start up, at least not at first. Also, not all AOS failure modes generate exceptional engine vacuum.
The engine's behavior when you remove the cap is normal.
I would advise *not* removing the intake manifold unless you absolutely have to. If the intake manifold is not leaking or otherwise a problem, best to let sleeping dogs, and an air tight intake manifold alone.
You can remove enough of the intake system up to the manifold to then remove the throttle body and check it for signs of oil or dirt contamination. This I found during the first AOS failure. The TB was oily and the butterfly valve had a drop of oil ready to fall off its bottom edge. A cleaning and reinstall fixed the engine stumble and mild idle hunting, for a while, but the symptoms came back as (unknown to me at the time) the failing AOS supplied copious amount of engine oil vapor from the crankcase to the hose connection just behind the TB. There was a lot of oil at this connection too.
The AOS proper could be ok, but its housing may have developed a crack, or the pleated rubber hose could have split, or the hose from the AOS to the manifold could be cracked. Any one of these could be the source of the oil leak and yet not be bad enough to generate any engine symptoms. Whether one of these possibilities is the cause is a job for you to eliminate each and every one.
The oil leak could be coming from somewhere else. Oil leaks are hard to trace cause these engines are in a quite confined and hard to work in space. Air flow around and through the engine compartment can blow oil up and even forward from its leak point.
Some places will wash/degrease the engine and then put a harmless dye in the engine oil. The engine is run and a black light is shined onto the engine and the oil leak area will glow when the black light hits the oil with the dye in it. Sometimes the oil leak is a tiny crack or pinhole in a hose. Other times it will show up as a bright but short thin line along a gasket or around a seal or plug.
Based on what you've posted I do not think you have enough to justify replacing the AOS. It may be going bad, but if so it has not gone bad enough to make it clear it is going bad.
I'm not in favor of washing these engines but sometimes one has to do what he has to do.
Thus you could consider washing the engine -- I use Gunk and spray it on a warm (not hot!) engine, let it sit, then rinse with if I can get it warm to hot water. I carry buckets of it out to the car or if I can run a hose to a convenient hot water faucet I do that.
Then after a good rinse start the engine -- serpentine belt will likely squeal -- and let it idle and warm up. Leave engine cover open. Let engine get up to operating temperature or close to it. Shut it off and let it cool enough you can work around it without getting burnt.
Then with a good light and a small mirror on a swivel stick look at engine and all the various external parts, hoses, lines, seals, plugs, gaskets, etc, very carefully for any signs of fresh oil seeage or leakage.
If you see none, take car for a drive. Just a normal drive but run engine up and down rpm range and again get it fully up to operating temperature.
Bring car back home and again let the engine cool. Perform the same inspection again and again look for the first traces/signs of an oil leak.
If you spot it chances are good where you spot it will provide you with a good clue as to just what is the source of the leak.
Caution: If at any time -- except immediately after engine start after washing -- the engine begins to run rough, emit smoke, exhibit any untoward behavior at all, shut off the engine immediately and arrange to have to have it flat bedded to a qualified shop for diagnosis of the rough running or other severe symptoms.
Sincerely,
Macster.
This is a source reference. Confirm exact model applicability in the original material.
