Throwing parts at it isn't the way to go. It's a rare thing to have a water pump not flowing coolant. The most common issue with them is the shaft seal goes bad and they leak.
Also, the T-stat doesn't regulate the engine temperature...the temperature marked on the T-stat is the temperature that it open to full flow to the radiator. Once the engine gets to the T-stat temperature set point it opens and stays open.
I'm with others, have the radiator looked at...
Mike B
