17 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHPossible AOS issue?
Leading reported evidence
Replace oil about a month ago and only
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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Performed · outcome unconfirmed · Original poster
I changed the oil about a month ago and only use premium gas on my cars.
Replacing the AOS with the engine in the car is a major PITA DIY project, one you will never want to repeat....unless you are going to pay someone else to do it.
Leading evidence: 'Replace oil about a month ago and only' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, 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.
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Performed · outcome unconfirmed
I bought a new black cap for the car and used the old yellow one for the manometer ( I never liked the yellow cap anyway).
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Suggestion · Original poster
I would love to hear your opinion on this before replacing the AOS.
Replacing the AOS with the engine in the car is a major PITA DIY project, one you will never want to repeat....unless you are going to pay someone else to do it.
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.
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Suggestion
Yes, replace the AOS lines; they're likely to be brittle.
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.
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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.
Replacing the AOS with the engine in the car is a major PITA DIY project, one you will never want to repeat....unless you are going to pay someone else to do it.
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.
17 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: 20261026T112012Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
You Tube
This is my first post here!!! My 2003 996 C2 is smeeling a bit of coolant and has a fairly strong vacuum on the oil cap. If I remove the oil cap (almost impossible to do it with the engine running) cars idles rough and white smoke starts to come out of the exhaust. I did some research here and it looks like and AOS issue.
I would love to hear your opinion on this before replacing the AOS. Do you believe this is an AOS issue? There is no CEL and no codes on the ECUs...
Anything else that should be replaced with the AOS? Car has 120k km or 75k miles.
Thanks! Appreciate any inputs!
You have the yellow crud in the oil filler cap - an indication that you haven't been driving the car much. Or have you? My advice would be to go put some fresh high test gasoline - Shell 93 or Chevron 93 and drive it! Have you changed the oil in the last 6 months? If not, I'd recommend changing the oil/filter. Then, if you're still getting lots of smoke out of the tailpipe, get yourself a manometer reader. You should read about 5 inches of water. CR Tool makes one of the best units out there, but I'm sure there are cheap manometers on Amazon that you can make work. If the manometer reading is way off the 5 inch of H2O, then it's time to have the AOS changed out. Good luck!
Thanks for the response! I bought the car recently and it is a low mileage example. So I don�t believe it was driven very often. But now this is my daily drive. 🙂
I changed the oil about a month ago and only use premium gas on my cars. The manometer idea is good. But I would also have to buy an oil cap to adapt the hose, correct? Thanks again!
CR Tools offers a complete kit for the 996, but it's expensive.
https://www.rmeuropean.com/Products/...1-MFG1245.aspx
Many people configure their own manometers with used 996 oil caps on eBay. Works the same, but many pros insist on CT Tools for accurate manometer readings.
Again, since the car hasn't been driven much. Go out and drive it! After a full tank of gas is burned up, do another tailpipe check.
You don't have to buy an extra oil cap to use the manometer (unless you just want to). Just drill and tap your existing one , install fitting and when done place a vacuum cap on the nipple, simple.
Do you do a lot of short drives? Not getting engine up to temp and keeping it there to cook off condensation from the oil will sometimes cause the yellow gunk you're seeing at the cap. Here's a thread on building a manometer.
Manometer
I agree with those above. It looks like the gunk under the oil filler cap is a result of not driving the car long enough and getting it up to full running temperature. With the oil/filter change, it sounds like you are doing everything right except for driving more frequently and longer runs. Before jumping to an AOS conclusion, a simple check with a digital manometer will tell you where you are. Replacing the AOS with the engine in the car is a major PITA DIY project, one you will never want to repeat....unless you are going to pay someone else to do it.
Gunk under the oil filler cap is also highly dependent on colder ambient temperatures in combination with more humid air. Even when driving the car for a longer time.
I live nearby the coast and as soon as night temperatures start to drop in the fall the gunk starts to appear little by little. Even when driving regularly long distances. When I visit my parent for a longer weekend (they live 3hrs driving more inland) the funk is gone after 2-3 days. The air there is significantly drier as there is no direct humid air supply from the sea.
Nothing to worry about. Just ignore.
Unless it starts to look like a big mayonnaise pot.
The CR Tools manometer is actually a Dwyer Series 476A with a CR Tools sticker covering the Dwyer logo. You can buy the Dwyer unit for $80.00 and use the $180.00 savings to buy a cap and some tubing.
$80 Dwyer 476A-0
That�s a great deal! Ordering one. I went for a longer drive today and the engine feels really solid. Tomorrow I will check with my UV light if there are any coolant leaks (added dye yesterday to the coolant).
I read the AOS replace is a pain. But some people say it was not a big deal... 🤷🏼*♂️
I live in Ontario, Canada so cold weather is a factor, specially this time of the year.
There are a few other things I have to do to sort the car out. Great to know I can count on great responses here! Thanks every one!
I finally got to use my new manometer. I had trouble finding a correct fitting. The manometer takes a 3/16 or 1/4 inch tube but all of the fittings I found were much bigger on the other end. I bought a new black cap for the car and used the old yellow one for the manometer ( I never liked the yellow cap anyway). I couldn't center the fitting because it was two wide for the channel. Having it off center prevented me from screwing it all the way in but it's in far enough to be tight. I hit the outside of it with hot glue. It's not pretty but it works. Is it normal to read a bit higher when cold? It was about 6.5, then I took it for a short ride and tested again and came up consistently right around 5.0.
