So today I was driving home and I thought I had fighting squirls under my hood. Upon closer examination the sound seems to be coming from the pulley above the power steering pump. The pulley is connected to something that looks like a pump and has a big round disk attached to it.The sound is intermittent, but still worries me. Could it be a bearing going out that i can change? can someone tell me what it is? or am i completely wrong in my diagnosis? Please keep in mind this is a California truck.