Here is a picture inside the waterpump housing. You can see the obvious shiny area where the old composit impeller was rubbing. If you look closer, you can see the pitting in the metal that is a telltale sign cavitation is happening which clearly it is. Cavitation also happens on cylinder wslls due to engine vibration. Caterpillar engine coolant is designed to minimize cavitation from happening. This condense atop of the engine is there to condense steam vaporization pressure caused by the various sources of cavitation and lower cooling system pressure by condensing steam vapor back into liquid.
