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FZP
Paul Ricard


Joined: 18 Jan 2015
Posts: 3359
Location: Cheshire


PostPosted: Sun Feb 24, 2019 7:38 pm    Post subject: Whistling noise at just above idle Reply with quote

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?
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arthouse
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Joined: 20 Nov 2018
Posts: 29
Location: Suffolk


PostPosted: Sun Feb 24, 2019 8:02 pm    Post subject: Reply with quote

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 🙄
 
  
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kas750
Reims


Joined: 31 Mar 2013
Posts: 4435
Location: Chorley lancashire

2006 Porsche 911

PostPosted: Sun Feb 24, 2019 8:05 pm    Post subject: Reply with quote

Yep try turning the ac off
 
  
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Paul Ricard


Joined: 18 Jan 2015
Posts: 3359
Location: Cheshire


PostPosted: Sun Feb 24, 2019 8:17 pm    Post subject: Reply with quote

AC was off as was trying to keep up with a 550bhp M4 Surprised
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
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deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6526
Location: Brighton


PostPosted: Sun Feb 24, 2019 8:23 pm    Post subject: Reply with quote

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
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Paul Ricard


Joined: 18 Jan 2015
Posts: 3359
Location: Cheshire


PostPosted: Mon Feb 25, 2019 4:49 pm    Post subject: Reply with quote

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?
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arthouse
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Joined: 20 Nov 2018
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Location: Suffolk


PostPosted: Mon Feb 25, 2019 5:45 pm    Post subject: Reply with quote

No different with oil cap loose?
 
  
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Paul Ricard


Joined: 18 Jan 2015
Posts: 3359
Location: Cheshire


PostPosted: Mon Feb 25, 2019 6:32 pm    Post subject: Reply with quote

Tbh that's the one thing I didn't do whilst I was looking.
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segart
Nürburgring


Joined: 28 Jan 2015
Posts: 404
Location: Jersey - Britains South Sea Isle


PostPosted: Mon Feb 25, 2019 7:00 pm    Post subject: Reply with quote

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
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deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6526
Location: Brighton


PostPosted: Mon Feb 25, 2019 7:03 pm    Post subject: Reply with quote

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 Smile
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Paul Ricard


Joined: 18 Jan 2015
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Location: Cheshire


PostPosted: Mon Feb 25, 2019 7:13 pm    Post subject: Reply with quote

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.
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deMort
Long Beach


Joined: 21 Mar 2015
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PostPosted: Mon Feb 25, 2019 8:18 pm    Post subject: Reply with quote

Im afraid you cant .. fly by wire these days .. electronic actuators .

The car is in control and not the driver !!
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Paul Ricard


Joined: 18 Jan 2015
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Location: Cheshire


PostPosted: Tue Feb 26, 2019 12:05 pm    Post subject: Reply with quote

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.
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deMort
Long Beach


Joined: 21 Mar 2015
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Location: Brighton


PostPosted: Tue Feb 26, 2019 7:30 pm    Post subject: Reply with quote

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 Embarassed
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Paul Ricard


Joined: 18 Jan 2015
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Location: Cheshire


PostPosted: Tue Feb 26, 2019 7:58 pm    Post subject: Reply with quote

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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