my 97 LS is making a strange rattling noise that sounds like its coming from the power steering pump. Sometimes is does it sometimes it dont. Usually it has just been when I'm backing up and I turn the wheel all the way, and then if i let go a little it quits. When I start my car it sometimes does it too for a little while then stops. But here lately it has been doing it while driving at an idle like at a stop light. When I press the gas it goes away. Does anyone know what this annoyance could be?