2008 Suzuki SX4 power steering noises

I recently bought the car about 7 months ago. Its still warrentied but thats comming to an end. The problem i'm having is my car makes a whinning sound (every now and then getting more and more) while turning. It sound like the pump is out of fluid. I've inspected the problem and it sounds like the power steering pump is making noise, the fluid level is fine. I added a little but it wasn't below the low mark. I've had my car in to the dealer twice now and they can't replicate a problem(because it doesn't do it all the time). I don't believe it effects the steering of the car but it does whine and make alot of noise once in awhile. What would you think the problem would be or how can I check it or have the dealer check it. Any ideas? Thanks Brian