Air Oil Separator

[Jim Russo]

I presently own a 2003 Porsche 996 Targa with 41,000 miles. All maintenance parts requiring replacement have been addressed. The Air Oil Separator has not been changed and is the original part.
There are no issues with the car and ir runs well. When should I replace the AOS on my car?
Thank you to all.

[JFP in PA]

when a digital manometer says your crankcase vacuum level at idle exceeds 5-6 inches of water.....

[matthewb0051]

I just replaced my AOS, it only took me 2 1/2 years.

From what I read recently the AOS is a 6 year part give or take. Also read from several forums that new ones have a high failure rate.

I had my IMS done in 2017, car had 35k miles or thereabouts. I told the mechanic to replace any wear items. I guess that didn't mean the AOS to them... while the engine was out and it was easily accessible. After they got finished with IMS they called to say the AOS had failed on test drive. So they had to drop the engine and do it.

Pretty sure the 2003 has the AOS with two bolts on top, which I think is easier to replace. Drop the engine down as far as you can and take off the intake (leave the coolant tank in place). It was harder on the Cabrio due to space but on Targa you should have lots more room. I could probably do mine in an afternoon now.

Word of warning: there are several coolant connectors that are plastic. Don't look at them too hard or they will break, let alone if you touch them they will surely break. Also the SAI canister near the AOS has a little pipe for a vacuum line, it will break if you barely touch it. So just be prepared to replace some odds and end plastic parts.

[Str8Razr]

Those plastic coolant connectors break and if you have a cabriolet, you will be engulfed in steam at the first stop sign. If you have coupe, you may not notice until it is too late. Replace them.

[rfuerst911sc]

If you are not a member of Rennlist you may not know about the UAOS or ultimate air oil separator . The inventor Skip was a Porsche mechanic and the system he invented has two key features .

One is he relocates an AOS diaphragm to a location right up by the throttle body . If/when the diaphragm ruptures it is a 10-15 minute replacement as it is very easy to get to .

Second the diaphragm that Skip uses is twice as thick as the original and more pliable so it is much less likely to rupture .

Plenty to read about his setup on Rennlist if you care too .

[Jim Russo]

Thanks to All for your responses regarding the Air Oil Separator on my 996