xel996

I heard that whining sound from another thread and most of the guys posted there that it might be the secondary air pump.

jumper5836

could be the idle belt tensioner bearing

iornman86

it is the AOS, remove the oil cap and the noise should go away, alto the car will run rough

This one was of the first issues i had with my car. the AOS was defective it was putting way too much vacuum on the crank case causing air to sequel past the seals making god awful noises.

the increased vacuum causes the oil pressure to read loader causing it to flicker on and off at idle

least this is what happened to my car.... replace AOS and everything went back to normal

ctrzaska

Either that or a check valve is stuck partially open or clogged a bit, or some secondary air hose has cracked. I tend to think it's the AOS. It's in today for another check... had someone under it with a stethoscope and it's not coming from the engine itself, which is a good thing. We shall see.

Jake Raby

AOS..Especially if it only does it at and just above idle
Its killing the oil pressure and volume to the bearings as well.

ctrzaska

Don't ask me why I remembered NOW to follow up on this thread, but for those who endured the pain of the vid and responded, I figure I owe at least the courtesy of a verdict, albeit late... it was a biblical failure of the AOS. Other than the several hundred to fix, it was almost worth it to view the stunned/bemused/horrified looks of those who had the pleasure of hearing this first hand.

And now off to swap out DME relays and fuel pump fuses in the hope that'll fix my latest issue of the engine cutting out. Old oil sludge ain't helping either. Sigh.

Thanks again all.

Bdub

I have a similar noise on my 2000 996. When I pull the dipstick out, the sound goes away. The sound also goes away when I open the oil filler cap. I think it is a vacuum issue - right??

Also, after messing around open the oil filler cap yesterday, I started the car today and there was a lot of smoke - whitish, grayish. Yikes - but I'm hoping this is some kind of blow back.

OR - does anyone think this is leading to an AOS swap?

Thanks for any replies.

DBJoe996

Well documented on here. AOS failure=white smoke from exhaust. You are in for an AOS replacement.

kromdom

+996. To Bdub: check out this video:

Bdub

That is it exactly! Thanks for sharing, bringing it in Monday.

Bdub

Thanks, I hope the whining noise is associated with this too. Last winter, when the whining noise started, the 'stealership' replaced the serpentine belt and pulleys. Which of course was not the problem. Then I was told it was a fan that blows hot air in to the intake when it is cold. That still might be not working right, because occasionally there is sort of a screeching noise when I start the car. One thing at a time I guess. First, a new AOS!

moon48

Hi,

What about similar symptoms (the noise) but in a 997.1 GT3? Removing oil cap while the engine's running does not make a change to this noise.

Thank you
Jacek