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Old 01-02-2013, 09:09 AM   #1
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Another failed AOS!

Hi All,
I replaced my AOS a few months back after the white smoke on start up issue. It was all sorted with a genuine part from the Porsche Shop - 1hr total - Tidy.

However, last week after a 'spirited' run, overtaking an SUV, 3rd gear 4-5k, the old girl left a huge trail of blue smoke behind like a James Bond smokescreen!
This leads me to believe that this is caused by vacuum of oil created under load, being dumped into the intake.
After a quick check under the lid, no obvious oil leaks and no level drop, but there is oil in the intake so it appears to be getting through the AOS membrane.
I have two theories for the premature failure and any help with this would be appreciated:-

Firstly, when I replaced the aos in July, the aos>intake tube (5 on image) was cracked, I replaced with flexi hosing (automotive water type) - non porous but can flex under throttle load, could this be a factor in stressing the aos membrane (uneven vacuum)?

Secondly, the PCV - this is the main feed from the crankcase>aos and it does appear to commonly block up. If this is blocked when I find its location, could it cause uneven vacuum in the aos membrane also?

Stuff to do so far....

I am picking up a new AOS and CPV from Porsche Sheffield in the morning,
Remove and clean the throttle body/intake of any oil residue
Change the plugs as the old ones are all now evenly contaminated.
Replace the aos>intake hose with genuine 'hard' tube.
Clean MAF as it could have oily residue on it also

The PC valve (number 6):


Is there anything you guys recommend checking while I am in there?
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Last edited by srad34; 01-02-2013 at 09:58 AM.
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Old 01-02-2013, 01:56 PM   #2
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hi srad.
i bought this part (and part 4) as part of my AOS replacement.
i thought it will be smart to replace the whole system "while in there".
found out that the line (part 4) goes from the bottom of the AOS (located on the bank 1 side) to the valve (6) that's located on bank 2. the whole "plumbing" is going under the intake manifold.
so i have the parts on my shelf, hoping never to use them. removing the manifold looks like a PITA.
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Old 01-03-2013, 06:14 AM   #3
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Hi Meir,
Thanks for the feedback, I went to my local Porsche dealer today and had a chat with one of their Technicians as I was asking if the valve was stuck open, could this be a problem, he was not aware of this being a common fault but it is possible. Worth checking and cleaning.
I need to locate it first!
New AOS and spark plugs bought, tomorrow, the intake manifold and TB are coming out for cleaning so I will search for it then, plus fit the new aos. The aos>manifold pipe was out of stock so I plan to vent it into a filter and block off the manifold. The tech said the DME will adjust fueling to suit so this should work fine.

Its NOT a permanent change as I have ordered a new aos>intake pipe to replace mine, but if it clears up the smoke, that's got to be a bonus!
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Old 01-03-2013, 02:21 PM   #4
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Quote:
Originally Posted by srad34 View Post
Hi Meir,
Thanks for the feedback, I went to my local Porsche dealer today and had a chat with one of their Technicians as I was asking if the valve was stuck open, could this be a problem, he was not aware of this being a common fault but it is possible. Worth checking and cleaning.
I need to locate it first!
New AOS and spark plugs bought, tomorrow, the intake manifold and TB are coming out for cleaning so I will search for it then, plus fit the new aos. The aos>manifold pipe was out of stock so I plan to vent it into a filter and block off the manifold. The tech said the DME will adjust fueling to suit so this should work fine.

Its NOT a permanent change as I have ordered a new aos>intake pipe to replace mine, but if it clears up the smoke, that's got to be a bonus!
if you intend to remove the manifold please post some pics and impressions.
as far as i understand from reading the forum, the bank 2 manifold is not that bad to remove. that should get you to the valve.
the real pain is removing bank 1 manifold in order to replace the long pipe (part 4).
again, never done this, so will appreciate your impression based on your experience.
good luck, and keep us posted.
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