High pitched metallic ringing / whistling noise

[uumode]

I noticed a quiet high pitched metallic ringing / whistling noise coming from the engine bay of a W210 E240 (somewhere) when parked up and idling with window wound down or standing on drive.

The irritating high pitched ring almost creates the same emotionally jarring effect as chalk on a blackboard or a knife on a dish. (but not quite)

Just a sort of constant eieeeeeeeeiieeeeeeeeiiieeeeeeeeeiiieeeeeeeeeeeiiieeee!

 

[NormanB]

Could be dirt on your drive belt - you can clean it at idle if you are v careful and know what you are doing with a brass brush.

Of course it could be something else entirely.............but at least you will elimanate that.

 

[uumode]

Thanks, I noticed if I accelerate into the garage, the volume increases.
It's sounding rather like the test card transmission when the TV channels go off at night eieeeeeeeeiieeeeeeeeiiieeeeeeeeeiiieeeeeeeeeeeiiieeee!

Hopefully, it is something simple like dirt on drive belt.