There is a noise coming from near the bottom of the radiator on the driver's side. It's a whirring sound like a bearing is going out on an electric motor. I believe it's the electric water pump that pushes water through the heater core because it only makes the noise when the heater is on. If I set the climate control to 60 there is no sound. The moment I turn it up the sound comes back.

Anyone ever have trouble with this or ever replace this part? #2 in the link below.

Would air in the system cause it to sound like that? I don't have any overheating issues at all so I don't know if it could be air in the cooling system.

The car is a 99 528i with 179K. Hills, CA
'99 528i Sport, Black/black