My first
Porsche
was a 2005
Cayman S
(unfortunately now long gone.) During my ownership I replaced the air oil separator (
AOS
), just like many owners and many on Planet-9.
I recently bought a 2007
Boxster S
with 75,000 miles on it, and it had the original
AOS
. It was not long before the smell of oil permeated the cabin on every drive, and almost every drive produced a Check Engine Light with P2187 and P2189 errors (generic too lean condition at idle, banks 1 and 2). I immediately suspected the
AOS
even though there was no "white smoke" on cold start as is often the telltale sign of a problem. Apart from the rather non-specific CELs, the idle was irregular, and the car ran rough at idle, and was hard to take off at a traffic light in1st gear, feeling like it was about to stall. (I share these "symptoms" in case you have experienced, or are currently suffering from, them.
The way the
AOS
is connected to the intake makes it a perfect cause for a too lean condition. The air intake system runs as follows: air filter, MAF, throttle body,
AOS
returns, plenum. The pressure and air flow in the intake after the throttle body creates a vacuum in the
AOS
which separates the crankcase air and oil and returns the (hopefull not oily) air to the intake. My MAF was clean and dry (no oil residue), but the
AOS
return pipes were full of oil, the classic sign of
AOS
failure. Upon inspection it looked like the
AOS
might have "sprung a leak" and was letting oil return to the intake as well as excessive air into the intake causing the lean condition. The
ECU
/
DME
was struggling to keep the A/F ratio in good shape, but just couldn't.
The new
AOS
has given the
Boxster
a totally new feel - smooth idle and smooth running, with the sensation of more power coming on without hesitation.
Replacing the
AOS
is not easy (much easier in a
Cayman
than a
Boxster
!), but it can be done with patience and a review of the video how-tos on YouTube. On 987s with high miles like mine, I consider it a preventative and prudent repair.
I hope this little note might help someone.
The preemptive repair is a good idea, and I did exactly that, but then here's the story...
I have a 2008
987.1
Boxster
2.7, and last year, even though there were no symptoms of failure, I had the
AOS
pre-emptively changed. (I also did the same with the water pump and thermostat. I had the indy shop use
Porsche
parts rather than aftermarket.) Mileage was about 104K kms when the work was done.
My subsequent issue is that for the first time in its life the car is now using oil, it's drinking about half a litre in 5000km. I know that's not much, but until the
AOS
was changed it used zero.
Does anyone know what the cause might be? Maybe a defective unit? Might it be drawing oil from the crankcase? I will definitely have the workshop do a
manometer
reading and otherwise check things out when I return for my annual service in a couple months... but if anyone has any suggestions or has experienced something similar it would be great to know more before I go in.
AOS
, bore scoring and oil starvation are the downfalls of 987S. Your workshop
manometer
might spot a higher than spec vacuum reading.
My relatively new to me 07 CS smokes on startup but not every time. I changed the
AOS
and there was some oil in the return hoses so it might have been bad but replacing it didn't fix the issue. About every 6th or so time I start the car I will get a lot of billowing smoke that lasts until I back out of the driveway. Otherwise most of the time it starts without any smoke. Doesn't seem to matter how cold it is or how long it sits between starts.
Before I did the
AOS
I was also getting an occasional misfire on startup so I took out the vvt solenoids and tested them. I cleaned the front vvt solenoids and replaced the rears and it hasn't misfired since. But I still get the white smoke every once in a while. I have vaccum from the oil fill tube so I don't think it's bore scoring unless it's only one cylinder and the engine has to stop with that piston in the right place to let oil leak by. Does the
AOS
not work correctly in some conditions? Could a new
AOS
be bad? I have 64k miles.
What else can it be?
Thanks everyone
Flat6innovations.com should help you out. There is a full 6 video listing on that web site about bore scoring.
I'm not a flat 6 expert (yet) but do read a lot and love to tinker with my '06. I don't think an occasional burst of white smoke is a sign of trouble. especially when you describe it happening every 6th start, that could be just condensation in the
exhaust
. could be, not saying it absolutely is, but if you had a serious problem then it would be more consistent.
