About 1/4 of the way through the winter my engine started making a whining noise when I would first start it up. It would go away once the engine was fully warm but now it is starting to stay even when the engine is warm. When I lift the hood up and listen it sounds like the power steering pump. I checked the fluid level and it looks fine along with the belt tension. Any ideas? 2002 ext 4x4 108K miles.