I own a 2001 MBZ E320. I am getting noise coming from what I thought was my idler pulley, so I pulled the serpentine belt and ran the engine. The noise went away and I found the idler pulley's bearings were bad and replaced the pulley. I checked the remaining pulleys and all appeared well. I reinstalled the belt and the noise returned. I re-checked the pulleys and found some "play" in the pulley attached to the waterpump. Does this "play" mean the water pump and pulley need replacement? It should also be noted I don't see any leaking or heating issues with the colling system.