Replace the AOS

My 987.2 has done 105k so i changed my spark plugs today and decided to check the hoses on the AOS for oil. There is a thin film of oil at both ends of the hose, also the cars smokes a little on start up, Given the oil in the hoses I assume i need to replace the AOS ?

Maybe. Mine is definitely shot in my 987.1 , I had oil dripping out of the lines when I disconnected. Previous owner looks to have neglected the maintenance. Fun thing is it seems like the oil going in and burning up seems to clog up the cats so I'm actually also having to replace the cats as well. I dunno for the $100 bucks or so it costs for one it's worth the piece of mind at that mileage to just replace it imho.

Is there an easy test? Just digging into my 2012 2.9 Will be doing the air filter tomorrow, so will get a chance to look things over.

There is a thing called a manometer test. Not entirely sure how it's done.

Yes, there is a nice test video here: Note that the reading you get differs between generations, so be sure to look for the right values.

I believe overfilling can lead to some of the described conditions Etropy. For those of you who bought used there's no way to know how well the oil was monitored or treated. I was always taught overfilling was hard on seals too for every car. Since I do my own oil changes, I leave the oil purposely a bit more than 1/2 quart low. Then I warm the car, check for leaks of course and go on a test loop, once warm I go to my level garage and run the check. I keep it one bar lower than all bars lit. I slowly top it a little at a time till I reach this goal because it's easy to get to all bars lit which then makes draining a bit of a chore to correct. Even if it's two bars low till you I get it straight I don't sweat that, its fresh oil going through a new filter, I just carry the quart topper.

So for those who have responded here, there are two different AOS 's going on. The 9A1 engine from 09 and later, which does last longer than the M97 engine AOS . The manometer valuves are different for these motors, so pay attention. For those of us with the M97 engine , please use the original Porsche AOS , as latest trials show a big difference in the membrane used that is the key element inside. On ********, 996 there is a thread "oil pressure instability" about the use of a genuine Porsche AOS , which really works well in a recent monitored track event that describes the unexpected positive use of the original Porsche AOS in high g force corning (1.8 g) and oil levels. Slakker is testing a new Hartech oil pan with the Porsche AOS with excellent results.

I've got a 2011 Base model that I've been a ton of preventative maintenance on. Although I've had no smoking on start up, etc., I did see oil residual/droplets inside the vent line that connects from the AOS to the throttle body elbow. I also saw oil residue on 2" portion of the vent line. I replaced the AOS for good measure and then pulled apart the original AOS (definitely the original one to the car. The AOS rubber diaphragm was not torn and looked fine. The diaphragm spring was fine too. That was hardly any oil residual in the AOS other than in the area of the diaphragm. The car currently has 72K miles. While I had the vent line out, I inspected it very closely with a magnifier. Sure enough, there was a hairline crack in the vent line right where the oil residue was on the outside of the line. It was not observable until I bent the line slightly to open up the crack which was about 1/2" in length. I taped up the cracked area of the vent line with electrical tape and have ordered a new one. What sucks is that I see two oily residue spots on the vent line on the front of the engine as well. My guess is there may be cracks in those spots too. To replace that line requires removal of the central intake manifold. I put electrical tape on those two areas best I could (very tight area) and will replace that line this summer. When I got the car back in October 2022 from Porsche Colorado Springs, it was CPO'd and just had an oil change. The oil gauge indicated full. I drove it 700 miles home. Over the course of about 1,000 miles, the oil level dropped to 3/4 and has stayed there for 2,500 miles and that has included often hard driving. If I had to guess, the oil residual in the vent line is the result of the prior owners keeping the oil at the full mark.

A puff of smoke is normal for flat engines. If my 986 is any indicator? You'll know when the AOS is really toast, it looked like I worked for Orkin spraying for mosquitoes back to my house.

To the best of my knowledge, nobody makes a more reliable replacement . For a slight upcharge in acquisition this one might be. But you can replace the cheap one like your toothbrush and be money ahead. 987.1 Motorsport AOS Kit | Renn Part

I don't know about the 987.2 , but on the 987.1 I've seen failures as early as 65K miles. Also, check the AOS lines for leaks as well as it's brittle and hard plastic.

I believe this thread belongs in a more technical subforum.. so it's being moved. HANG ON!