Diagnosing RPM related high pitch whine/noise

[notorious]

Hello all,

My D2 FL suddenly developed a high pitch whine, which can be clearly heard when I sit in the car while the car is parked.

Noise is clearly RPM related, but it is difficult to say where the noise comes from. Not even sure at this stage if it is from the front or from rear of the car. I appreciate there is nothing from rear that can generate RPM related noise, but simply judging by ears it is impossible to say where it comes from...

It is high pitch whine that kind of disappears with higher RPM perhaps because frequency goes so high that it becomes undetectable by human ear. Engine is revving a bit after 2000-3000 rpm, so it hides the noise too.

I tried to switch aircon on and off and play with steering wheel. Noise pattern does't change when I do that. It seem to be RPM related only.

* Is this bearing noise? No bearings in my car were changed yet.
* Can the RPM-related noise/whine be generated by smth other than bearing?
* In your experience which bearings fail first on D2? Any usual suspects?
* What are the best methods to isolate and diagnose problem?
* Any great tools I can buy that will help me to listen and isolate sources of noises/whines?

Any advice will be appreciated.

[The_Laird]

* Any great tools I can buy that will help me to listen and isolate sources of noises/whines?

Any advice will be appreciated.

Try this: http://www.ebay.co.uk/itm/MECHANICS-NOISE-LOCATING-STETHOSCOPE-CAR-REPAIR-ETC-stethescope-/111256397412?pt=UK_Hand_Tools_Equipment&hash=item19e765e664

[notorious]

Thanks Jim.

Purchased the Stethescope: http://www.ebay.co.uk/itm/321265618327

[Delboy]

High pitched whines i my experiences have turned out to be bearings on things like fan belt jockey wheel /Idler Pulleys.

Once you your ear thing comes it will be easy to pinpoint it if it is a bearing race complaining.

You could try the old screwdriver handle held to your ear with the tip resting against the area you want to listen too.

[notorious]

Thanks Delboy +++

[Goran]

Sergey, you could also try just removing auxiliary belt from the crank pulley, run engine for a few minutes on battery only, if no noise it was something on the auxiliary belt.
I did this method on my previous S8. I had 2 noises, one was a timing belt roller, the more fain noise was the water pump.

[notorious]

Thanks Goran. Excellent idea.

Is it easy to remove aux/serpentine belt on our engines?

[Goran]

It was very easy, if I remember correctly I reduced the tension on the tensioner and only removed the belt from around the crank pulley, making sure it wouldnt get caught in it with engine running. I left it on all the other auxiliaries, too lazy to take it off completely.

[notorious]

And when I put the belt back how do I make sure it is correctly tensioned?

Is the tensioner automatic with a spring or should I just pre-tension it by hand and then tighten a bolt?

[Goran]

Very good point. Here is the Elsa Win guide for a 2001 3.7 A8.
I need to copy all of these instructions to PDF / Word at some point.
Have a careful read through, to me it seems the belt is simply tensioned by releasing the tensioner locking tool (or a drill bit, etc).

"fit onto tensioning roller last"

[notorious]

Thanks Goran

[notorious]

Breaking news: The whine appears to be coming from under the dash.

I just discovered if I hit the dash my left hand the whine will stop. Hit the dash again it starts again!

I'm completely puzzled...
What under the dash can produce strong RPM related high pitch whine?

[Architex_mA8tey]

Are you sure it's not related to the Audio system? Turn off the RNS-e and see if it's there then?

[notorious]

No, not related to sound system.

[PsYcHe]

Mouse? Squirrel? Small child?

Is it in the middle of the dash? Could be the climate unit, or maybe the drive in the RNS.

[notorious]

It is unclear where exactly it comes from.
Whine frequency is directly proportional to engine rpm...