Our relatively new-to-us 2010 XC70 T6 with 104k miles has developed a noise coming from the drive belt area and I'm trying to determine its exact cause. It sounds like a bad bearing and I just replaced the tensioner and idler pulley since they appeared to have some wobble in them when I started investigating the noise, but this did not help. My next thought is either the water pump or the power steering pump but I'd like to figure out which one is most likely making the noise before I blindly replace both of them. Is there a way to determine which one (or neither) is making the noise? I tried listening to both closely with a tube up to my ear and the other end near each component but with no luck. When I had everything out of the way for the idler pulley I turned the power steering pump by hand and it seemed like there was an unusual noise but I can't be certain it is the cause of the noise I am hearing when the car is running.

If it does indeed need a new power steering pump, water pump, or both, what are the best options in terms of cost and reliability? I see genuine Volvo remanufactured power steering pumps going for over $500 online and Cardone remanufactured for significantly less.

Thanks!