AOS failing?

Friends, Hi. I have a 2011 987.2 Cayman with the 2.9L engine and PDK . Bought it last spring with 58K miles and have driven the car nearly every day since without issue—it runs great. Yesterday I noticed an oil drop on my garage floor. Never had one before, so today I looked around to try and figure out what's going on. I don't know the name of the part where the oil is dripping from beneath the car but it's a connection point for a large tube leading from the plenum/throttle body (pics below). I immediately came on here and read several old threads on tracking oil leaks like this and they all seem to point upstream to the AOS. So, I pulled the hose on the AOS. There is definitely some oil collecting in there, but I'm not sure what that means. As noted above the car runs like a champ, with no signs of smoking, oil loss, hesitation, rough idle, lagging, etc. I'm a fairly handy do-it-yourselfer and have no problem replacing the AOS but not an expert mechanic and have no idea if that's the right place to start. Any and all insights and advice would be greatly appreciated. Thanks in advance, George P.S. The sequence of the pics goes from below the car to the engine bay above, a close up from above, and then two of the AOS hose.

Well, I either posted this in the wrong spot or I'm universally despised. For peace of mind, I'm going with the former. Anyway, for anyone interested, I replaced the AOS yesterday. That was pretty easy, thanks to old posts here and YouTube videos. Toughest part, of course, was the Rubik's Cube-like challenge of removing the old part and inserting the new one. That's a head scratcher for sure. It was lovely today and I went out for a two-hour spin along one of my favorite local mountain loops. The car still runs great, so I guess I didn't screw anything up. Will be watching closely to see if the little oil drip that prompted the AOS replacement has been resolved. If not, I'll keep digging. Best, George

I just replaced mine, and while in there, walnut blasted my intake valves (64k miles). When I took the plenum apart to remove the intake manifolds, there was quite a bit of oil sitting in the plenum gaskets/clamps. My hoses had oil in them too. Could have been either of those. Cut my old AOS apart, and it looked fully functional and new :/ One thing I’ve always heard to be cautious of is not overfilling the oil during changes. I try to leave on little tick on the measuring bar open. I’ve had to drain oil many times I don’t recall the reasoning on the overfill problem. To fully disclose, my last oil change was way overfilled because I wasn’t paying attention. 5 trips under the car to get it to the right level. That sucked.

Hope that clears things up for you. I think I may be good to go, but am planning on cleaning the plenum and air intake areas this weekend—mostly out of curiosity. Just changed my oil and filter and was very careful about the level.

@JSnTX - How did things shake out in the end? Short version is that I just bought a 987.2 that was woefully overfilled by the previous owner (2+ quarts) -- I'm guessing because they went by volume and didn't drain the car level. That being said, I've got the same thing where there's a bit of oil on the floor after driving...and less so after draining off the excess. Any idea where the leak was and/or anything else you needed to do? @George_L -- if you want to weigh in as how things worked out for you, I'm all ears. This makes me think that it involves the AOS, although my AOS is likely just fine (no cream cheese or goo anywhere). Car runs like a top, from what I can tell.

@foodbiker Replacing the AOS seems to have remedied my oil seepage issue. Like you, I didn't have any recognizable symptoms of AOS failure. As I have no more leaking, I guess replacing the part fixed the issue before recognizable symptoms occurred. What I did see was a small drip of oil forming where the air intake manifold and the mass air flow sensor housing connect. (Best view of that connection is from beneath the car, looking up past the oil filter housing.) Like I said, after replacing the AOS, the oil drip has stopped. I will keep monitoring things, of course, but I am optimistic.

Mine didn’t have a leak, I replaced the AOS as a precaution since I had the intakes off for valve cleaning. As George mentioned, I would suspect it was leaking at one of the intake plenum connections. Both sides of my plenum (where connected to the intakes) had oil pooled in the clamp, which is outside the rubber gaskets. I suspect if I’d let it go long enough, eventually I’d see some drips. I probably should have replaced those two gaskets, but I didn’t and only cleaned them well. The gaskets were a pain in the rear to reinstall with the clamshell clamps, but I think that was preferable to trying to remove/install the AOS with the plenum/intakes in place.

I think the key to your and my problem with oil is the overfill. You’re kind of stuck with disassembly and cleaning. My 987.2S runs so much smoother now that the valves are clean. No more 2nd gear stumble when pulling out from a stop.

This is a great help, you two!!! I’ll likely get in there at some point soon and do some major cleaning then. It may have to wait until the spring as garage temps are getting really cold… Stay tuned for more questions once I get in there. Thanks again!!!

the intake system can get a little oily on our cars according to the tech's I've spoken to. As a preventative measure, I changed my AOS as felt it was due after 10 years. As most of you have experienced, it is very easy to over the limit when filling so be patient when filling.