987.2 C exessive oil in air intake plenum

Hi All, A few days ago I noticed oil drip on the garage ground. I opened the engine lid and found exessive oil on the heat exchanger just below the air intake pelnum, then the engine bock, as well as the other side of the plenum. I took off the plenum and found tons of oil inside the plenum. I actually changed the AOS around 1.5k miles ago. When I did the inspection when I bought this car (used) the only problem I found is oil around the MAF area and downwards. I searched on the internet and thougt it would be the AOS issue. I have seldom cases getting smoke when starting up but throttle sluggish when taking off and air sucktion when lifting engine oil cap , so decided to change the AOS . At that time, I saw no trace of oil below the air plenum. After changing the AOS , the throttle sluggish issue when taking off is solved. The air suction keeps the same. But since it has no any infulence to the drive, I am satisfied. After I found the oil on the garage ground I change the AOS again because I also learn that the AOS failure is quick sometimes. Then i droved about 300 miles this weekend I found quite amount of oil on the heat exchanger again! I read a lot threads saying they changed the AOS because of issue similar to mine as above but hardly saw anyone saying the issue remains after changed the AOS except this one: Oil In The Intake And he ended up changed the engine under warranty after 3 AOS change. Is it common? Should I be worried about it because I think i may affect the throttle body and MAF because there is also oil there. I am even think about selling it Thanks!!!

You may want to check for valve leaks. My original engine did the same thing and upon removal we found that two of the cylinders showed signs of burnt oil. Maybe an indication of requiring a valve job as the valve seals do go bad.

Hi. You might mention to us the year/model of your 987, there are a number of different engines that were used in the cars and some of them have flaws that could cause this sort of issue. You've only owned it around 1,500 miles? How much oil has it used in that time period.

If it is the case, should I see smoke when engine start up?

Sorry, it’s the base model with 2.9L engine

And I'll repeat my questions: You've owned it how many miles? And how much oil has it used in that time? The 2.9 is considered a reliable engine, not prone to bad things happening. It might be something as simple as a leak. I wouldn't have replaced the AOS twice - they don't fail quickly - they fail from miles/use. When you say you found oil on the heat exchanger - that's the external water/oil heat exchanger?

What I found on my 2010 CS was if I filled the oil to the full mark (not the top of the gauge overfill mark, just the full mark) it would tend to consume oil and I'd get some oil in the plenum which would seep out from the two rubber sections at the left and right of the plenum and end up on the top of the head. Solved this by (a) torquing the clamps on the plenum rubber to spec, and (b) keeping the oil to one mark below full.

I have owned it for 2.8k miles So far the oil level is still at full mark But I think it going to be one bar below since when I measure the oil level it sometimes shows one bar below the full mark, but most cases it’s full. Yes, I mean the water/oil heat exchanger under the air intake plenum.

I am actually noticing the very same thing with my 987.2 2.9. Oil pooling up in the same place as you described (but only on the passenger side, not the driver's side) just below the intake plenum. The leak was traced to be coming from the intake oval gaskets, I already changed them and also AOS but still some oil will seep through. A Porsche mechanic said it's kind of known thing, oil getting into the air intake and seeping past those oval gaskets. Also even with a new AOS some oil will go through, you can see in this YouTube video Porsche Cayman S 987.2 oil catch can update - YouTube just how much oil can go in the intake plenum even with a new AOS and few miles driven. I don't have any performance issues or oil consumption in 1.5 years and 10k miles. I do get the occasional cloud of smoke at start-up, sometimes when cold, sometimes when warm but I've been reading it's a known thing with early 2.9 engines (mine is February 2009). What I did to minimize the oil going past the AOS is I switched to RedLine 5W40 which has the lowest NOACK evaporation score (6%), so the stress on the AOS is less and filling it only up to the middle mark.

Yeah, that's where mine was seeping. Retorquing the T30 bolt holding the clamp on the rubber piece to spec (3.5 ft-lb, 5 Nm) seemed to help.

Ok, thanks! I will check the torque to make sure it's up to spec.

@lalawoo_chen You could check the vacuum at the oil cap, just to make sure the AOS is fine. Note however that the normal vacuum with good AOS for 987.2 is higher than 987.1. This is one mistake people make, thinking the gen 1 and 2 should have the same vacuum. On the 9X7.2 and 9X1 Porsches, the engine crankcase vacuum reading is normally in the region of -14.0" to -16.0" H2O (Inches of water). When an oil separator fails, the crankcase vacuum can rise to -20.0" to -25.0" H2O, or even much worse (-30 to -40.0" H2O) depending on the extent of AOS failure. M96 & M97 Nominal crankcase vacuum is -5.0" (-4.0" to -6.0") of H2O (not HG) . MA1 Nominal crankcase vacuum is -15.0" (-14.0" to -16.0") of H2O (not HG) . See this article for more info Tech Tuesday: Understanding the PCV System and AOS - by Tony Callas (constantcontact.com)

Greetings everyone, reviving an old post in hopes of some fresh insights. I have a 2010 Boxster S . It runs fine, no clear signs of smoke (other than a dirty exhaust ) , but it has a bit of a drinking problem. Last time I checked, with cruise speed driving, it burned around 0.4 liter per 800-1000 km. (One bar on the digital readout) but with heavy driving … ufff I’ve seen it show one bar missing with as little as 200km, or probably less, but I’m not sure now. I initially had an oil leak that was pooling oil on top of the engine, but, the oil pooling didn’t match the amount of oil missing, and I soon found plenty of oil inside my intake. Got a new AOS … Problem didn’t go away. I eventually fixed the external oil leak but to be quite honest I’m not sure what it was as I was trying 2 solutions at the same time. It got a handful of experienced mechanics super confused as to where the oil was coming, but eventually I stoped it. Can go into that into more detail if someone is interested. Anyhow, at some point the oil burning got worse… someone suggested I check the AOS because perhaps it failed again. With some research I found this thread, measured -21.85 inH2O in my crankcase - measured from a modified oil filler cap . “ahah, it’s the AOS ” So now I’ve replaced it (while doing some more work on the engine - installed IPD intake with larger TB) … and after removing the old AOS I’ve opened it to see if I spotted some damage on the membrane and, nope! It looked fine. Not really sure what I was looking for, but there was no visible signs of damage on the membrane. Got the new AOS in and… -27 inH2O ! What the hell? Ive asked a friend who’s a Porsche tech and he was at a loss. Because lower vaccum can be caused by a bunch of things, but higher vacuum could only be the AOS . Ideas? I’ve considered that I installed also a new intake plenum, but how could that affect the crankcase vacuum? I'm at a loss. I’ll have to drive it for a while to check what happens with the oil level (good thing I have two relatively long trips coming up), but the strangest thing is that my ECU logs shows no more knock events at high rpm (7k+) which I believe were being caused by oil in the misture resulting in a lean mixture. ECU logs show promising results, but crankcase pressure shows no changes or even worse values? Another possibility, could I be using the manometer wrong? But I mean… there’s two tubes and not many options, what could be done wrongly?! if you’ve read this far thank you! Thanks in advance for any feedback

Aren't we still going to the Perf AOS for these problems. Wrong term but too many years ago to fully remember right name.

Sorry, I’m not aware of what that might be. I only know of a better AOS for the pre-DFI engines, not for these engines :/

Motorsport version was used on my 2006 CS I guess that's pre DFI