2005 MC with 5 speed manual. New Issue. Vehicle overheats only when stopped at idle for a few minutes, (in line at drive through lane). If I rev engine, or once I leave and drive normal speeds, temp returns to normal. I can hear radiator fan running very load when it's overheating, and after I turn the engine off. It also runs loader and longer than I ever remember it running after turned off. All fuses are good, relays are good, coolant system and overflow tank are full. Oil level is good and no signs of leaking under vehicle.
Ay Ideas? Could this be water pump? What controls low speed fan?

 

Sounds like you might just have a bad thermostat. Also I'm not sure if your car has a two speed fan like my 03, but if it does there is a large resistor in the fan assembly that may have burnt out causing the low speed not to work.
Good Luck

 

wouldn't a bad thermostat just stick and not allow the emp to come back down to normal?

do you need to take the fan assembly out to find the resistor?

 

I had the same exact problem(overheat when stopped, cool down once it started moving) with my old R53, definitely a bad thermostat. I had the dealer replace mine since it was under warranty at the time. If a thermostat is bad is doesn't necessarily means that it is seized as you describe, it just does not open and close at the pressures it should. Thus when you start moving again the air coming through the radiator cools the engine and the symptoms go away.