Porsche 996/997 Air Oil Separator Replacement (1998-2008)

The engine air-oil separator is an emissions device that is responsible for collecting residual gases and vapors contained inside the crankcase and funneling them back into the intake manifold where they can be burned in the combustion chamber.
This reduces the overall emissions of the engine.
On the 1998-2005 Carreras, the engine air-oil separator is located at the top left rear corner of the engine. For the 2006-2008 Carreras, Porsche redesigned the system and moved the AOS to the top of the engine under the right side intake.
When the separator fails, you will begin to see a large increase in the overall vacuum in the engine crankcase. In the most extreme cases, the air-oil separator fails to separate the oil from the air, and oil is then sucked into the intake manifold. Oil in the intake system is not healthy for the engine and it can foul spark plugs and destroy catalytic converters at the very least. The failure of the air-oil separator is often but not always, accompanied by huge amounts of white smoke exiting the vehicle's exhaust and a generally poor running engine. You may experience a check engine light (CEL) as the oil being drawn into the intake can affect the mixture level. The oil cap may be very difficult to remove when the engine is running due to high vacuum levels. In addition, you may hear a high-pitched squeal from the engine when it's running because air is being sucked in past the crankcase seal due to the extreme vacuum inside the case...
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[@Engineerboy100]

Excellent presentation! Thank you for posting!

[@pelicanparts]

Glad you enjoyed it!

[@nicolascraig5829]

Very thorough once I get the part in hand I’m giving it ago.

[@pjay3028]

Can I check about the M97 engine. Everything I see in parts catalogues says the 997 3.8 with the M97 engine always had the newer style AOS, from 2005 onwards.
That suggests it was only the early 3.6 997 engine that had the old style AOS at first?

[@pelicanparts]

You didn't mention what year and model vehicle you are working on.
With your vehicle info handy, give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.

[@pjay3028]

@@pelicanparts thanks, it's a 2005 997 Carrera 2S 3.8. I have managed to look into the engine bay today and I confirm that I can see the later version AOS on the car so I think this may suggest that all M97 engines have the later part which I think slightly contradicts the information on the Pelican parts DIY webpage?