AOS Mystery Leak - Fix Now or Monitor

I've had my 996 for a little over a month, and when I got it, the PPI didn't show an oil leak nor where there any spots on the flat concrete pad where the seller parked it. I got an oil change on 2/18 and parked the car on the more inclined part of my driveway and noticed two things...wiper fluid leaked out (it was filled to the brim after the oil change) AND I developed a slight drip on the driver side by the chain tensioner nut (pic of it all cleaned up and no drip in the last 24 hours). I've since been parking it on the flatter part of the driveway and watching for a couple of weeks now, and it will sometimes go days without a drip. Below is the piece of cardboard from the past 2 weeks that I've rotated a few times and marked the drips. I got new front tires and took it in for an alignment yesterday, and my indy took a look. They said they couldn't pinpoint anything, but did find oil sitting in the crevice on the crankcase (used a mirror) and they cleaned it out. They said it's most likely a leak on the left side of the AOS where it connects to the crankcase and it was pooling and dripping down. They will need to get in and explore to figure it out which will be the equivalent of installing a new AOS ($1K)...a new one was done about a year ago. In 1 month and 500 miles, the virtual dipstick still reads full bars and there is no smoke whatsoever at start or at any time. Is this is a "get it fixed ASAP"...or "continue to monitor it" type of situation? I know these cars are $$$ to maintain and I budgeted for that when I bought it, but I don't want to stroke checks for minor things that necessarily need attention right away. Thanks for the insight.

Just some friendly advice, if you do have them change out the AOS please do not use a stock one. ONLY install the UAOS from Skip (porschetech3) here on Rennlist. You can buy it from the UAOS website or from LN Engineering. The stock ones can fail almost immediately after install or last years, it's a gamble either way. With the UAOS it's way more robust. Please read some of the post in the "UAOS install/tips/tricks" thread. Good luck.

So it's been a week since my indy cleaned up the oil that pooled as well as the area under the car around the chain tensioner and vario cam cover...and not a drop of oil on the ground or any showing up in the aforementioned area. Any thoughts on what would made the oil pool in the first place? Could it have been overfilled a bit? It's still showing full bars in the dash after a month and 500 miles.

Not knowing if you have a "real" issue or not, I would keep driving and monitoring the car to see where the leak comes from, allowing you to pinpoint if you have to replace something or just tighten it up. Going thru the same exercise with my car now as I am replacing parts for its next 20 years. You can always test your aos with a manometer. A few threads on Rennlist explain the process. One thing I have learned with the car is that small drips can happen from time to time if you dont drive the car enough.

One part to keep in mind is the corrugated plastic line with the snap fitting to the AOS. Those become brittle and crack and will leak. The snap fitting can also come loose if it wasn't fully engaged. It's about an hour job to replace the line if it's defective.

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Please tell me how you can replace that AOS line in an hour. Just to get to it you have to remove everything from the TB back, remove the drivers side intake manifold, and snake that AOS hose from the AOS through the passenger intake manifold to the breather connection on Bank 2. If you have a better way, I would sure like to hear it. To the OP: monitor or test it with a manometer. It will let you know when it is done. My AOS was leaking coolant so had to replace.

Thanks for the tips. The AOS was replaced in the last year, but not sure about what parts (i.e. hoses) done as well. I'll keep monitoring.

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FWIW, take a look on Amazon at a Dwyer 476A manometer for $104. You will have to get an oil cap and drill it to attach a hose fitting but it will give you a tool to measure your aos. I just went thru the same exercise and am wondering why I didn't do it sooner. Ultimately I will replace my motorsports aos with skips UAOS with drainback relatively soon, but it was one more part that I could test myself as I planned my next round of replacement parts. Good news is its fine, bad news is it will eventually go. The UAOS is an all around better product so it's what I will do. As a side note, make sure to take a look at your oil cooler, which has shown to be a solid product, but they are known to leak at the seals, especially after 20 years. It's something that I am watching on mine and will probably get it replaced shortly as well. Remember, there is a juggling act between what you must do because you have a problem, what you should do for prevention of a problem, and what you want to do just "because". Good luck with it.

At my last oil change I saw some oil leaks (not really drips, just weeping around seals). It stopped shortly after, I think you can safely just monitor it for now. Regarding the UAOS: The original AOS is not overly fragile or bad in any way, just difficult to replace(done it twice as preventive maintenance....unnecessary in hindsight). The original have been the only option for decades and it works well. Now, since you don't need to do anything about this you should go ahead and remove the front bumper and clean out the radiators if you haven't already done that. Search the forum, there are good guides how to do it. Came to mind since I'm just about to do it before the hot weather arrives here.

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Except that what you don't know is that Porsche updated the factory AOS 6 times and is still crap. They even lowered the oil level by .5 qts in the 996.2 due to deficiencies in the AOS where it would gulp oil in the intake on high G-Force turns. And is so fragile that shops across the world who specialize in M96/7 engines started to recommend replacing the factory AOS every 3 years as a preventative measure. SMFH

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Do you seriously think Porsche would sign off a car which gulps oil in high G corners? If it gulps oil in high G corners it's: A broken AOS or worn/broken scavenge pumps or both. It could also be that you have modified your car with sticky tires etc so that it's not working as it should anymore. At the same time, read post #792 here, and explain how this person have done +60 trackdays and podiums on local races...with the original AOS: https://rennlist.com/forums/996-foru...bility-53.html

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Of course ,I'm 100% absolutely positively serious about it, unlike you.( Who just takes out his azz) Porsche even sent out TSB,s out this in 2002 and the reason they changed the dipstick and recalibrated the dash. They most certainly had signed off on it, then they redesigned it. Everyone who tracked there car knows this. Slacker has been lucky as has Jason by running a lower oil level and experiencing oil pressure drops but using high quality thick fresh oil to luckily survive. Jason is now running the UAOS with much higher oil level and less oil pressure drops, so will Slacker. They, unlike you , know a better design when they see it.

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I didn't find it necessary to remove the intake, just the TB and crossover. The old line was secured to the other crossover with something resembling a wire tie, but I just snipped that loose and secured the new one with a wire tie. Pretty sure I put the new line in the same path; I used a length of coated bundling wire to help fish the new one back through. Seems like I had to move some other small stuff out of the way, i.e. positive terminal connector, but nothing really challenging.

3 weeks now and not a drip. The area where it was dripping is still clean as it can be.

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Great news. Do your self a favor and at least test the aos with a manometer or an easy thing to do would be to remove the oil cap while the engine is running and warmed up to see if (1) its tough to get off with alot of vacuum and (2) once oil cap is off, the engine begins to stutter. If so, you have a failing aos. If not, then you can run these 2 tests every so often.