Passat 125 TDI white noise at idel and "half ignition"

[mebius9]

I'm hearing this "white noise" or faint whine/beep/hum when ever I put the car in "half ignition"
(state before the actual ignition) and at idle...

It sounds like some sort of small high speed motor operating...

Anyone else experiencing this?

[mebius9]

I did some googling and found some bloke suggesting that it is secondary water-pump that circulates coolant around the engine after shutoff
Is this right?