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Whistling noise at just above idle

FZP

FZP

Zandvoort
Joined
18 Jan 2015
Messages
5,877
A little help please.
After a spirited run this morning, pulled up to a town car park, and the space I was reversing into had a wall behind it. I could hear a strange whistling noise that would make its presence heard when id blip the throttle as I was reversing in. I can't really hear it above 1500 rpm. I did search and the suggestion was to try and remove the oil filler cap. If you couldn't open it, then it's the AOS. I could open it no problems, interestingly, when you open the oil filler cap the engine revs rise, and drop back once closed again.
So any ideas as to the source of my whistle?
 
I had a similar issue today after a long drive out in the sun today.

Mine is almost like a 'beeping' noise, after asking on the fb Porsche owners group, someone suggested AOS, and to loosen the oil cap with the engine running, which I tried, and the noise stopped. My oil was a little low too so it's either that or I'm in need of AOS.

I'm guessing your noise didn't stop when you loosened the cap? Another suggestion I had was about the A/C, was yours on or off? Might be worth trying both on and off to see if there's a difference.

Was going to post a video of my noise but can't 🙄
 
AC was off as was trying to keep up with a 550bhp M4 :eek:
As for the noise, at idle it's not present, it's when you get to that 1500ish rpm that it's at it's most noticeable. I'm not sure if the engine/exhaust noise drown it out or it stops. I'm assuming it gets drowned out.
Someone posted a video of it a few weeks back, a red 997, but for the life of me I can't recall where....Rennlist/FB/Here/PH.
I'll have a play with it tomorrow to see if I can replicate it
 
X2 things im thinking .. well actually three ..

AOS is on its way out .. a whistleing noise is air being sucked in due to a restiction in the aos.

A/C .. turn it off .. so econ and see if the noise stops .. if so then its A/C related .

Its a one off due to god knows what
 
So I've had a good sniff around and I'm going to change the description of the noise from a whistle to a rapid chirp. I got Mrs P to replicate the noise whilst I has my head in the engine bay.
Observations are:
Chirp present once warm only
Is only around that 1-1.5k rpm
Noise originates from the top rear centre of the engine bay
AC on or off made no difference.
Does this narrow down possible fault?
 
Tbh that's the one thing I didn't do whilst I was looking.
 
I had this very thing on my 996. It took an age to solve it. A high pitched squeaky whistle, only when the engine was warm, and in my case at 2100rpm. It drove me crazy. Turned out to he a very slightly misaligned airbox which was not quite properly seated.
Rick
 
Drive belts can make a similar noise ..

At work i would remove it and test ( start it and listen ) .. i would also spin each idler pully as well .

Edit to say the AOS is in that position .. does it do it with the oil cap off ?

As always .. a sound clip would help :)
 
I'll see if I can get a video of it during the week along with trying out the oil filler cap.
Out of curiosity, how does one rev the engine by hand. When Mrs P was blipping the throttle, I couldn't see anything move. If there was a way, it would make it easier for me to get the video done.
 
So today I had some errands to run so took out the 911. Got up to temp and the chirp was there. When I opened the oil filler cap, there was some suction, but easy enough to open.
I think this is leading to an AOS on the way out by the info provided. So updated symptoms are:
Chirp at just above idle
Location of chirp is top centre near the firewall
Slight suction when opening the oil filler cap.
 
Excellent write up on G2 AOS replacement here ..

https://www.6speedonline.com/forums/997/401440-997-2-3-6l-aos-air-oil-oil-mist-separator-diy.html

It shows the location very well and it fits with your idea of were the noise is ..

How ever .. if you remove the oil cap then i would have thought the noise would stop .. you havent mentioned this .

On these cars and the AOS is pretty good .. but when it fails it makes a hell of a noise .. but not many fail .

I would still make sure its nothing thats driven off the drive belt before jumping in and replaceing this .. it can be a bit of a problem fitting the new one ..

I have broken a new one whilst trying to fit it :oops:
 
The noise is only present just off idle at that 1-1.5k rev range. When I opened the oil cap the only thing that happened was a rise in rpm slightly and some suction as I cracked the seal.
Although that link you sent is quite easy to follow, I don't have the confidence with this. I'd hate to drop something down the intakes or something silly. The location of the AOS in the pic is approx where I heard the noise come from.
I might bite the bullet and drop it in to the guys to sort as it's a 2 man job to control the throttle and locate the noise. Thanks for the answers, always appreciated.
 
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