Is my AOS going? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

S3adrag0n · 04-11-2010, 06:27 PM

Clikman, mine is doing the same. Hopefully we'll get a reply from those who had AOS failure. Rightnow, would be a great time for me to replace mine if it is.

Steve Tinker · 04-11-2010, 09:16 PM

I think what you are experiencing is quite normal.
Even with a new AOS, when I removed the oil filler, I could hear a vacuum being pulled and it lowered the idle rpm a little.

944boy · 04-11-2010, 09:22 PM

When my aos failed it was VERY difficult to pull the cap off. It was far more vacuum than normal. I pulled the cap off the other day and experienced similar results to you, but I could actually get the cap off. When mine had failed, it was blowing huge amounts of smoke on every start up and I had a squealing noise from the motor. I think your good.

eightsandaces · 04-12-2010, 02:41 AM

With my car being white is was easy to watch the AOS go, near the end the rear cover would get a ever so slight coating of oil, not anymore since a/o replacement.

S3adrag0n · 04-13-2010, 09:16 AM

944boy, that definitly help. I've heard you should not get any air sucking at all to ok to have air sucking. With your AOS replaced and is doing what mine is doing, I feel a lot better so I'll go and stump on my gas peddle today! Here's to you...

blue2000s · 04-13-2010, 10:31 AM

In order to reduce oil contamination, foaming and moisture build-up and minimize pressure build-up, the car's crank case is under a slight vacuum by a connection with with intake manifold. The AOS sits in the middle of this connection to collect most of the oil that is pulled from the crank case and returns it to the engine. It is completely normal to hear or feel a vacuum when opening the oil cap.

S3adrag0n · 04-13-2010, 01:42 PM

Thanks blue2000s, that's a great explainaton! Here's to you too..

PS. I was out there in CO (Lafayette visiting my in-laws) a couple years ago and man, did I feel bad visiting them a week earlier and missed the Porsche Parade.

yimmy149 · 05-22-2010, 11:54 AM

Did you even read this thread? Your answer is right here:

Quote:

Originally Posted by blue2000s

In order to reduce oil contamination, foaming and moisture build-up and minimize pressure build-up, the car's crank case is under a slight vacuum by a connection with with intake manifold. The AOS sits in the middle of this connection to collect most of the oil that is pulled from the crank case and returns it to the engine. It is completely normal to hear or feel a vacuum when opening the oil cap.