2012 BMW X5 50i Whining Noise
 

2012 X5 50i, After about 1200mile, I started to hear whining noise 15-20 seconds after stopping at traffic lights or stuck in traffic and only after driving about 25 minutes. Then iF I park the car for over 20 minutes, the whining noise comes back after another 25 minutes driving. It appears the noise coming from the very front under the hood. I took the truck to the dealer, they went road test after I waiting there over 30mins. They said they can only have 10mins road test with me, so they did not hear the noise. Please help

I had the same behavior on my X5 2012 around the same mileage. I didn't go to a dealer; wanted to wait and see if it gets worst. Fortunately, it disappeared after a few weeks and never came back.

Cooling fan?

It sounds alot like the cooling fan. If they can only do a 10 minute test drive, why not go drive the truck around for 20 minutes before the test drive. Then let the truck idle for 5 minutes before they get in. This should recreate the issue per your description.

Why not open the hood and listen to where the sound is coming from. It should not be hard to hear if the sound is audible in the vehicle.