I bought a 2009 base Cayman (PDK) with 38,000 miles. Took it in for service, shop said they found a serious oil leak, the AOS needed to be replaced. Done. About two years/10,000 miles later I see oil on the garage floor, take it in (different shop; we moved in the meantime), they say the AOS needs to be replaced. Odd, I say; they say, maybe a defective part. They replace it. Less than a year later, I see oil, take it back, they say it's the AOS. Very odd, I say; they say, maybe a second defective part. They replace it. Six months later--now at about 56,000 miles--they're servicing something else, see oil on the engine, say it's the AOS. Nope, I say. They replace it for free, clean the engine, I drive another 2,500 miles, no leaks, no change on the oil gauge. I take it to another shop for 60,000 mile service. They see a lot of oil, say it's the AOS. Not the answer, I say. They pull the plugs, use a scope, say the cylinders look fine. They say if the leak continues, maybe replace the engine. Surely there's a better way to hunt the problem down. Anyone have an experience like this?

 

I have no answer, but find it odd that it stops leaking for thousand(s) of miles after the AOS is replaced then randomly starts leaking again, then stops for thousand(s) of miles after the AOS is replaced again and starts leaking again, then stops for thousand(s) of miles after the AOS is replaced again, and starts leaking again, etc.

Someone with a lot more knowledge than me will chime in, but it also seems strange that if it's leaking that much oil there would be evidence of it at the place it's leaking from.

 

It's possible that it leaked slowly and steadily, but that there was no evidence for long stretches. In all this time--4 years, 20,000 miles--only once has the gauge indicated that the oil level had dropped, and it never dropped out of the acceptable range.

 

Yes, that is pretty wierd. If you want to be proactive, take off your engine cover and give the engine a good wash with a degreaser. Then purchase a dye product that is designed to add to your oil and will show up with an UV flashlight. Quite common to purchase at autoparts stores. Start checking your engine bay on a schedule that seems reasonable and try to really pinpoint where the oil is coming from. Armed with that info, you should be able to figure out what is going on. But yes, oil leaks that stop and start randomly are not normal. As you sense, if you aren't having to add oil, this is not a crisis. Just keep an eye on it.

If you've got an hour or so to kill, you can check out my 987 Oiling article.
https://newhillgarage.com/2023/04/14...tem-explained/

 

Mostly replying because I have a 2010 carman base with nearly 70k miles that has a damp tubes near the AOS, but nothing leaking, and am curious to learn more about this area. A related and maybe helpful question would be, how do you test the AOS for proper function? The only thing I’ve seen on the youtubes is people pointing to obviously torn diaphragms inside the AOS itself. A diagram of the hoses/air and oil flows would also be helpful to understanding more of the underlying issues.

Question for you - does this correlate to oil changes at all? And how high is the oil level? I see a lot of people showing the oil level at max bars and saying it is good, but the problem is you don’t know if you’ve overfilled at all and by how much, and I have to imagine this could contribute to crank case ventilation issues. One empty bar on the oil readout seems most appropriate.

i agree whole heartedly that the shop who said “if not the AOS, then replace the engine” is not approaching things well and should be treated with a healthy dose of skepticism and probably not used for a Porsche again…

 

Not odd, the factory AOS is notorious for not lasting long. If you don't want to replace it again get the UAOS instead.

 

@sasilverbullet The common AOS failure is that the internal membrane faults and large amounts of oil are sucked into the intake tract, with clouds of oil smoke out the exhaust pipe ensueing. Hard to prove but anecdotally, even this failure is rare, especially for non-tracked cars. And certainly not every 15,000 miles or so. But the actual AOS splitting open or something and leaking oil. I'm not buying it. That said, I challenged him to find the true leak source, using the dye, if he is up for it. And/or find another shop.

 

@azblues, you are too new to the forum to allow personal messages (Welcome to Rennlist) but I would like to give you some pointers via a videochat. If that sounds like something you want to do, text me at 919 604 2188. I'm in NC.

 

The 987.2 AOS is redesigned and much more reliable than the earlier cars. I doubt that's your issue.

Where is it leaking from? On my 2010 I was getting a bit of oil seepage onto the top of the right head, and also down from the MAF sensor upstream of the throttle plate (rear left of the engine). It's normal to get a little oil into the intake (even with a good AOS) but what I found on my car was that if I filled the oil to the full mark I got excessive oil in there. The intakes tubes slope toward the right head and down toward the throttle, so the oil flows that way and then can seep out through the rubber tubes where they're clamped.

I started only keeping it full to one bar below the full line and that greatly reduced the issue. I also torqued the metal straps on top of the intake that hold the rubber tubes to the intake runners to spec (Torx screw, 3.5 ft-lb or 5 Nm) and between those two things it eliminated the oil onto the right head.

 

are you running with you oil level at the top? I just went through this and I stopped running with my oil at the absolute full mark and started running with the oil at 1/2 gauge. Problem
solved

 

Helpful. It's possible that, this most recent time, at least, the oil was over-filled. I just changed it and have it at one bar below full, so we'll see what happens.

 

There's a concensus to run these engines with the oil sensor reading 1 bar from full, the system seems very easy to overfill and the results from doing so you will find oil in the intake manifold so doesn't bode well for any air/oil device, gl

 

It is a shame that Porsche didn't design the dash bar indication to flash or something if the oil is overfull. Certainly the sensor logic would allow them to do something like that. I did see the other day that it will flash when it is underfilled, i.e. the bottom bar will blink. This was after an oil change and I put in 5 quarts and turned on the dash, just to see what it would do.

From my observations of the M97 engine, I don't think a "little" overfill would push oil anywhere bad but the problem is you just don't know where you are at with the dash indication. I too try to leave mine a bar low but sometimes when I get in the car, it will show full, and then later revert back to one bar short. Talk about a less than precise measurement device!

 

I've just put the engine back in and wanted to keep the oil from prior before I did an at temp oil change, so I know it was one bar below. I'd only dropped the filter and lost about a jam jar full before taking the engine out, so I added a small amount, as well as prefilling the canister with the new filter. The first 6 readings after getting to temp were all blinking bottom line, had me sweating I'll tell you. Then finally it reported what I was hoping for, 1 bar below.

Now after the coolant fill fiasco, atleast I can do an oil change without stressing so much. And once your at the 1bar under mark, you can measure what comes out to hopefully avoid any issue by puting a similar amount back in. I'd love to know more about the levels inside the engine at overfill and you'd think there was more leeway if overfilling, but there was pleanty of oil in my intake housing so it has me thinking thats the only way that could occure as the AOS is fine.

 

I'm fairly new to Porsche cars and was surprised/alarmed to 1) no dipstick to physically see/check the oil, and 2) the oil "gauge" is not really accurate. Neither is the coolant temperature "gauge", but that's another thread.

My car is parked in a 1 car garage, and I have a wheel chock to stop it at the same spot. So, I know when I use the computer to check the oil, the car is consistently at the same level. The other day I came home and as soon as I got it parked, ran the oil check (which we know takes about 1 minute). It showed 1 bar low. I shut it down, took the groceries inside and put them away, which took about 5 minutes. I went back out, started the car and initiated the oil check process. It showed full - all 4 bars.

I guess that makes sense if the time I went inside gave the oil a chance to let gravity do its thing and drain down to wherever the sensor is. I'm not clear on how the sensor works or where it's located, but this seems like a plausible theory. I guess the point of this is, don't trust 1 reading of the oil status - take multiple readings. I think I'll do some research about the oil sensor and how it works...

Edit to Add - I found this description; "The oil level sensor is a long plastic rod that extends into the oil in the sump. It has 4 wiring connections (in a common plug) where the sensor emerges on the top of the block. Two wires measure a resistance corresponding to oil level and the other two wires measure the oil temperature".

It appears letting the oil drain back to the sump for a few minutes before running the oil level check will show you a more accurate level. What the part looks like -