I have a 2002 Volvo S60. My car has been making this sound, off and on, for a long time. It started when my car went over a hump at a gas station and this sound started. However, it stopped when I added power steering fluid. It comes and goes. When water gets up under the wheel, it comes back. It's been gone for a while. Recently, I ran over a piece of truck tire, now it's back. It stops when I am driving uphill and and gets louder when going downhill. It's NOT the brake pads, I just replaced them. I added brake fluid, no luck. It sounds like metal scraping on metal. I don't think it's wheel bearings. Don't think it's the rotor shield scrapping against something.

Any suggestions?