If your Fan is not starting, when engine is getting hot? It's not in the water system, it's in the electrics. It could be a blown fuse or a loose connection. Beware of putting your hands near the fan, if the engine is warm, because fans are now electric and can run even when the engine is turned off. Not run on a Fan Belt. 99/100 it's a fuse or a loose lead. Good Luck.
A Davies
June 2012