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Old 07-06-2016, 08:24 PM   #1
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Boxster smoke bombed this evening - but not sure if AOS?

On the way home from work the car started making a loud whining noise that sounded behind the firewall. After it cooled down I looked at the pulleys, alternator, and belt but couldn't recreate the noise. Everything seemed to spin fine.

So then I went on a drive and after 10 minutes the whining started again then 3 minutes later under a bridge either the ABS or oil light flashed for half a second then 10 seconds later a giant smoke bomb went off. Tow home and naturally I figure it's the AOS. However I disconnected the AOS and briefly started it - I still have smoke coming out the tail pipe. I only ran it for 1 second, maybe 2 seconds repeated about 3 times.

Would the AOS ever make a whining noise? And does it just take a bit of runtime to clear the oil out of the intake? I've always had oil inside my AOS -> Intake tube so that is not a good indicator.

Here is the sound: https://youtu.be/A-4xQh45rTg

Thanks!

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Last edited by patssle; 07-06-2016 at 08:30 PM.
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Old 07-06-2016, 08:49 PM   #2
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I really don't think an AOS would make a sound like that. To me that seems more like a bearing of some sort. Hopefully someone more versed in the myriad of M96 noises can chime in.
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Old 07-06-2016, 09:09 PM   #3
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AOS, just a bad vacuum leak. Just because you disconnected it doesn't mean it will just stop smoking like that. It has failed internally and oil has bypassed it, hence the smoke. Just replace the AOS and you should be fine.
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Old 07-06-2016, 10:17 PM   #4
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Hello patssle,

first, the sound quality of your video seems to be extremely poor. So diagnosis won't be right.

If the noise on the video is like in real life and if it's only at a special rpm i would say water pump bearing failed. To make shure remove the firewall cover, remove the belt and than check every component driven by the belt (water pump, pulleys, alternator, ac compressor…). In general the bearing will do a noise when you turn the component and or will have axle play.

This is the failed water pump of my other car. https://youtu.be/SXfJ5tTlvT4

Made a similar noise at 2K rpm when bearing failed.

But that would be a complete independent problem to the AOS smoke bomb. Even if you clean throttle body and intake as good as you can, there will still be some smoke for some time.

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Old 07-06-2016, 11:37 PM   #5
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No bearings have failed. It is a vacuum leak. Caused by a broken AOS. I'd say 99% certain.
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Old 07-07-2016, 03:04 AM   #6
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John, i agree in general.

And i would also say that it's pretty uncommon that 2 completely independent components fail at the same time. But the sound reminded me of a worn water pump bearing. So i think it's not a bad idea to check.

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Old 07-07-2016, 06:47 AM   #7
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Yea when the aos fails will allow a huge amount of vacuum in the crankcase and sometimes will suck air thru gaps and bearings and gaskets and will squeel and make awhistling noise

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