whistling/squeaky Noise on 2001 BMW X5

A squeaky noise in the alternator pulley area. all pulleys were replaced, alternator bearings replaced, fan belt replaced the noise went away then came back two weeks later. I thought it might be the ac unit but why would the noise go away then come it possible that it could be the harmonic balancer if it has one. or the front fans. its like a low whistling sound

Asked by for the 2001 BMW X5
It sounds like the fan belt could be getting contaminated by coolant or oil. It is also possible the one of the pulleys is out of alignment causing a belt noise. The fact that the noise went away for a time after the belt was replaced leads me to believe the belt is somehow at fault. Contamination or pulley miss-alignment are the most common causes abnormal belt noise.
I had it checked out and they said it could be the harmonic balancer do you think this is possible. I appreciate your response on this matter. Thx