N62B48 noise with ignition on

[hias]

Hi everybody,

With ignition on (key in position 2) I am getting the following noise on my E53 X5 4.8is:
https://streamable.com/zhxi7

The noise seems to come from the front left of the engine bay (where alternator, cylinder 5, etc. is located).

With ignition key in position 1, this noise appears for about 5 seconds and then disappears. With key in position 2 the noise is there permanently.

I already disconnected secondary (electrical) water pump, auc sensor and butterfly valve actuator. These things are not causing that sound.

Did anybody of you experience the same noise or knows what is causing that noise?

[hias]

Forgot to mention it is the servotronic torque converter which is causing that sound. When I unplug it, the sound is gone. (servotronic too)

Replaced it with a new one (original BMW), however the sound is still there.
Do you also have that sound coming from the front left area of the engine bay with ignition on?

[Zoomit]

My 05 4.8is (130kmi) also has that ~1Hz sinusoidal electrical noise. I haven't tracked it down but am curious to hear if anyone else has!

[hias]

If it sounds like in my video and comes from the front left of the engine bay, it is the servotronic torque converter (32 10 6 788 212). Don't waste your time and money to replace it like I did.

[Emory39]

To me, it somehow sounds like the alarm. Its located next to the brake booster

[hias]

Yes, it sounds like an alarm. We used a special tool (something like that: https://www.google.de/search?q=auto+...AVpxOk4d2LM%3A) to locate the sound and when you touch the servotronic torque converter with it, the sound is very loud.
If you pull the plug, the sound (and servotronic) is gone