First, this really showcases the sound
www.memenest.com/enginesound.avi (right click, save as)
I have the belt cover off there, because I am particularly suspicious that it may be something to do with that assembly right there. Are there any of you out there with a keen ear that can tell me what the deal is? I just replaced the water pump since the mechanic thought it was a bearing in it, but the sound persisted.
