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Old 10-25-2013, 03:40 PM   #1
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Hi guys,

I recently replaced the air oil separator, which I believed to be original. When I replaced it, there was a lot of oil in the intake manifolds. After three months, there has been no smoke or anything, but while troubleshooting the P1128 and P1130 codes, I found a thin film of oil in the intake manifolds, more oil on the rubber boots, and a few drops of oil on the engine below the boots. My question is, if the AOS is working properly, is there supposed to be no oil at all in the intake?

Background info:
2001 Base, 127k miles, has had codes P1128, P1130, P0410, P1411 for a while.
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Old 10-25-2013, 04:21 PM   #2
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When I replaced the AOS I also found that the oil filler tube was leaking. This is sometimes caused by a failing AOS. Excessive vacuum causes the hose to compress and crack.

I think it also caused a vacuum leak because my 1128 and 1130 codes have disappeared since replacing the tube This would only explain the external oil

BTW Its a pain to replace.
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Old 12-18-2013, 05:01 PM   #3
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I replaced my AOS after the famous "normal" smoke on start up. I did NOT have a check engine light. I noticed the tube from the AOS to the intake had oil in it. I cleaned it when I changed the AOS. After a few weeks, the "normal" smoking started again. I pulled off the upper tube again and it had as much oil as before. I installed another AOS with the same results. Smoke after a few weeks and oil in the upper tube.

What I learned.. Just because something is called "normal" doesn't make it right. Do I think oil being sucked into the intake is right, no I don't. I went through 3 "good" AOS all with the same symptoms, so I guess it's "normal"

2000 Boxster with 26K. Oil level at full and changed to min with no difference. Oil changed from 0-40w to 15-40w with no differences either.

Hope this was of some help,
2000 Boxster 2.7
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Old 12-18-2013, 07:41 PM   #4
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Thanks for this guys. I had an inspection done with a very good Independent after I got my '02 BS. His one comment from listening to the exhaust was he thought the AOS was on its way out.

I ended up taking the throttle body off and yes...there was oil. Not dripping with oil....but a fair amount of oil.

Then I decided to take the throttle body off of my '08 Cayman....and guess what.....EXACTLY the same level of oil.

On both cars there is no excessive vacuum from the oil cap....so I am not replacing the AOS yet on the '02.

I just wish there was a VERY CLEAR description of what the normal level of oil in the throttle body should be. It's been a frustrating thing for me to research.
Current: 981 Cayman
Former: '02 BS and '08 C
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Old 12-19-2013, 10:46 AM   #5
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After replacing my "working" original on a '97 with 105K miles I have the same question.

Should there be ANY oil in the vent hose that goes from the AOS to the intake?

By design I would assume the answer is NO, but is there an authoritative source that can confirm this?

If that is the answer, seems a good way of checking the AOS would be to pull the vent line, on the intake side, and look for oil....no?
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Old 12-20-2013, 01:48 PM   #6
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I believe there should be very little to NO oil passing through the the AOS into the Intake. IMO, I think the factory AOS is to small to handle these engines. Look at the people that install the Motorsports AOS. It's bigger than the factory AOS and I've seen them report a diminish in smoke on start.
I think the AOS is a poor design due to the fact it passes through so much oil from know good units. I think Porsche knows this and just calls it "normal" instead of having fixing the problem. Maybe the Motorsports AOS was a fix. Just think of how much money it would cost Porsche to recall or admit a bad part. Instead it's easier/cheaper for the Porsche dealer to tell you it's "normal".

I'd be courious to see how much, if any, oil passes through the Motorsports AOS..

I worked at a Chevy and Ponitac dealer. When GM didn't have a fix for something yet... tell the customer it's Normal....

2000 Boxster 2.7
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