What type of power steering fluid are you using?

 

I'm using the stock power steering fluid, haven't ever replaced it.

 

I'd suggest that what might be happening is that the oil or grease you are applying is migrating up to the belt and this is what causes the noise to disappear. .

 

I've had this loud whistle for awhile now and got it looked at and they said it was my power steering pump.. Usually only could here it when the car was cold but it does it when its hot now.. Don't know if i should just replace it..