trayw before you put that belt back on grab your fan and see if you can wobble it front to back. If you can your water pump is toast. If not well get your self a Long Screw drive and start listening. If your water pump isn't bad ( I think it is) then my wild a** guess is that the fuel pump cam is lose! If it aint that then it is most likely the third from the front offset (not to be confused with recessed) muffler bearing.
Good luck and I hope you find your knock soon
