Air Oil Separator
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Air Oil Separator
I've seen this referenced in several places, but not sure if I have a clear understanding. 2009 C2 3.6L PDK. While replacing the air filters today I noticed the Throttle Body was pretty dirty so I opened the valve with my hand and noticed it looked wet inside. I then cranked and let it run for a few minutes, and opened the oil filler cap, which resulted in an immediately worse idle. Very rough and nearly stalling. Is this the sign of a bad AOS? It also smokes a lot upon start up and smoke for several minutes. Thanks for any advice. This is my first Porsche that I've had for about a month now.
Three Wheelin'
Joined: Feb 2017
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From: San Francisco
Welcome and congrats on the new 997! Sorry about the AOS. They are known to go. How many miles on the car? From your description it sounds like all the symptoms. Was there a lot of suction when removing the oil cap?
I dont know about on the .2, but on the .1 they are not that hard to replace. I think the part is under $200.
I dont know about on the .2, but on the .1 they are not that hard to replace. I think the part is under $200.
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The AOS on the .2 was redesigned and very unlikely to fail. What you're describing sounds normal. You can check it with a vacuum gauge.
The smoke on start up is most likely due to parking on a side to side slope. With the flat six, oil is sprayed onto the piston skirts. When you stop that oil lays in the cylinder on the crankcase side of the piston. If on a slope, that oil runs onto the piston rings and over time through the rings and into the combustion chamber. And yes, it smokes when you start it again.
The smoke on start up is most likely due to parking on a side to side slope. With the flat six, oil is sprayed onto the piston skirts. When you stop that oil lays in the cylinder on the crankcase side of the piston. If on a slope, that oil runs onto the piston rings and over time through the rings and into the combustion chamber. And yes, it smokes when you start it again.
Three Wheelin'
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From: San Francisco
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2009 C2S 130K miles.
I don't think my car has every really "smoked".... maybe a few times but it is hard to know the difference between steam and oil smoke. But... as Wayne noted.... I am always on flat ground. In my old Boxster S, I would get smoke on startup from two conditions (I had that car for 197K miles) 1) parking on a slope, 2) Starting and shutting it down real fast. Regarding no 2, for some stupid reason, I would park and shut down the car. Then start it up and shut it down withing 2 -15 seconds say to move it a few inches. This appeared to leave oil in the heads that then got blown out on next start up... Maybe the computer delays ignition for a half turn to squirt oil in there and the double shot of old and new gets it to blow through... I dunno, I can make stuff up all day, but that quick on/off definitely made smoke the next morning.
Flat 6 engines don't rely solely on gravity to remove oil from the heads, notice in the diagrams there is a sump pump in each of the heads to remove excess oil. Odd that Subarus do no have these pumps.
Peace
Bruce in Philly
I don't think my car has every really "smoked".... maybe a few times but it is hard to know the difference between steam and oil smoke. But... as Wayne noted.... I am always on flat ground. In my old Boxster S, I would get smoke on startup from two conditions (I had that car for 197K miles) 1) parking on a slope, 2) Starting and shutting it down real fast. Regarding no 2, for some stupid reason, I would park and shut down the car. Then start it up and shut it down withing 2 -15 seconds say to move it a few inches. This appeared to leave oil in the heads that then got blown out on next start up... Maybe the computer delays ignition for a half turn to squirt oil in there and the double shot of old and new gets it to blow through... I dunno, I can make stuff up all day, but that quick on/off definitely made smoke the next morning.
Flat 6 engines don't rely solely on gravity to remove oil from the heads, notice in the diagrams there is a sump pump in each of the heads to remove excess oil. Odd that Subarus do no have these pumps.
Peace
Bruce in Philly
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The AOS on the .2 was redesigned and very unlikely to fail. What you're describing sounds normal. You can check it with a vacuum gauge.
The smoke on start up is most likely due to parking on a side to side slope. With the flat six, oil is sprayed onto the piston skirts. When you stop that oil lays in the cylinder on the crankcase side of the piston. If on a slope, that oil runs onto the piston rings and over time through the rings and into the combustion chamber. And yes, it smokes when you start it again.
The smoke on start up is most likely due to parking on a side to side slope. With the flat six, oil is sprayed onto the piston skirts. When you stop that oil lays in the cylinder on the crankcase side of the piston. If on a slope, that oil runs onto the piston rings and over time through the rings and into the combustion chamber. And yes, it smokes when you start it again.
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From: Atlanta
Any ticking? This is a bit scary to think about given our 9A1 (997.2) engines make a weird set of noises if you listen carefully including ticking and tacking. There are some vids out there with recordings of piston slap... not a good thing... maybe pull up a few of those. Again, careful about jumping to conclusions... our engines make some weird-*** noises.
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Bruce in Philly
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Bruce in Philly
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I'll look for some videos on that. Once it warm up and the idle settles back down it "seems" to sound OK, but I don't really know what normal is. My local service shop told me it was running like it should.
Burning Brakes
Joined: Feb 2018
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From: Menomonee Falls, WI.
My 09 C2S (54k miles) makes a lot of noise, hard to tell if it's ticking or just general clatter. But the indie, dealer and tuner I take it to all say it sounds great and I should track it because it runs really strong. It certainly makes a lot more mechanical noise than any other cars I've owned in recent memory, even a Forester XT.
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Have a mechanic listen to it and do a vacuum test for the AOS. Anything that works can fail!!!
Do you burn oil and need to add between changes? I don't know if this really matters, but it is possible.
My driveway curves and slopes. If I park on the side sloped section (just moving the car or after a long drive) it smokes like a thousand camp fires on a rainy night. This lasts about 20 seconds which in dog years is like 2 hours. It takes minutes for the air to clear. At sunset it is most impressive.
So I don't park on the slope unless my garage is acting as a wood shop (or tile cutting shop for the last week). Yep, off topic.
Even with this smoke screen occurring on those rare occasions, without adding between changes I've had 7.5 quarts out and 7.5 quarts in at every 5K mile oil change over the 85K miles of my stewardship. So it is annoying but not a problem (environmentally debatable and definitely embarrassing).
Are you sure it's oil? Definite blue, or more white? Does the ambient temperature affect this? Does this happen after a quick on off, like filling with gas?
Do you burn oil and need to add between changes? I don't know if this really matters, but it is possible.
My driveway curves and slopes. If I park on the side sloped section (just moving the car or after a long drive) it smokes like a thousand camp fires on a rainy night. This lasts about 20 seconds which in dog years is like 2 hours. It takes minutes for the air to clear. At sunset it is most impressive.
So I don't park on the slope unless my garage is acting as a wood shop (or tile cutting shop for the last week). Yep, off topic.
Even with this smoke screen occurring on those rare occasions, without adding between changes I've had 7.5 quarts out and 7.5 quarts in at every 5K mile oil change over the 85K miles of my stewardship. So it is annoying but not a problem (environmentally debatable and definitely embarrassing).
Are you sure it's oil? Definite blue, or more white? Does the ambient temperature affect this? Does this happen after a quick on off, like filling with gas?