I have 2000 Durango that's has been overheating when idle but cools down when moving.

Replaced water pump and thermostat

 

sounds like a cooling fan issue, w/ the engine off spin the clutch fan by hand, if it spins freely(more than 1/2 a turn) replace the clutch, it should spin about 1/8 of a turn ( about one fan blade)

also check the e-fan (i think 2000 was the first year for that) make sure it is coming on, it will always be on w/ the a/c, if not try changing the relay in the PDC, if that doesnt fix it try jumping right to the connector to get it on, if it sill doesnt work then your gonna need a new fan.

 

+1 shrp, sounds like an electric fan to me.