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AOS Failure
JerryW - 9 months ago
MY 2003 S had the classic symptoms so I replaced the AOS, but for grins I tore the old one apart and was surprised to find the diaphram intact. This got me to wondering if there are other common failure modes with the AOS. Anyone with experience to share? My engine was smoking massively and the intake tubes were loaded with oil,and with the new unit installed all is well so I have to believe the AOS was at fault. Still...there is this lingering doubt!
It was the AOS.
One of the ways it fails is by a visual tear in the diaphragm.
But there are other ways, such as a detachment of the diaphragm from the sides of the housing and also having micro-tears which are almost invisible to the naked eye, yet allow for droplets of oil to pass through as liquid oil.
Happy Boxstering,

Pedro Bonilla
1998 Boxster 986 - 299,000+ miles: [www.PedrosGarage.com]

PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

^^^ what he said
Boxsterra - 9 months ago
there's only one possible source of oil upstream of the intake headers unless someone is filling the snorkel with oil, which I presume you would have mentioned

Edited 1 time(s). Last edit at 04/15/2021 10:11PM by Boxsterra. (view changes)
did the symptoms abate after you cleaned the intake and replaced the AOS?

If so, you did what needed to be done. No reason to overthink it.
Re: The proof ....
JerryW - 9 months ago
Yes.. the massive smoke bombs are gone and my neighbors are happy once more. While I have the floor, I have a couple of suggestions that might help anyone contemplating a DIY AOS replacement: the first is stolen from someone on YouTube and his stroke of genius is to use long nose vise grip pliers to release the lower hose spring clamp and to not release them until the hose is securely in place on the new AOS; and the second thought is if you find it difficult to insert the hose fittings into their receptacles, make sure the O-rings are not puckered out and not going in with the plastic fitting. Tuck the O-ring in with a thumb nail and life will be good again.
They make a ton of difference.

I also think buying new clamps for reinstall is a great idea.
Another way
Boxsterra - 8 months ago
Get one that comes with this little clip. You get everything installed, then position the clamp in place and pull the clip off.

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