Pulled into my driveway and heard a god awful sound. Almost sounded like valves against pistons. On further inspection I figured out it was the rad fan. I pulled the fan assembly last night. The outer ring of fan has cracked and was rubbing on the shroud. Is it possible to just replace the fan or do I need to replaced the entire assembly? Anyone have any part numbers of just the fan. It appears the fan comes off with a spring type clip. This thing only has 4700 miles. It must have gotten brittle from the heat cycling.