OK, so we bought a used 2001 Volvo S60 2.4T three days ago. Car seemed like it was in excellent condition. I've posted a couple of issues with it already and resolved one so far with your help. I do appreciate that.
Car was driving fine the first three days. Today, took a 100 mile trip and started having issues with the steering. Whenever I turn the steering wheel left or right, I hear a low whine that changes pitch according to how far you turn the steering wheel. I can also feel vibration coming through the steering wheel. I checked the power steering fluid reservoir and it looked fine. Plenty of fluid, red in color not the clear/green I read about on this forum, but nevertheless it is full. Any ideas?

BTW, the issues I'm having with the power steering only occur when the car has been driven a lot and has heated up. Once the car cooled down in the garage, I test drove it and the power steering worked perfectly.