My 01 Durango just started to overheat? Thermostat? And where is it at?

If you have the 5.9 engine, the T stat is under the nozzle where the upper radiator hose connects to the engine.

If you have the 4.7 motor, the T stat is behind the composite nozzle on the engine end of the lower hose.

Be sure to soak the bolts on the 4.7 motor nozzle and don't over torque them when loosening or tightening as they will easily break turning a minor repair into a major frustration.

Also, the 4.7 motor has a special "burping" process you must go through after servicing the cooling system to purge air from it. Otherwise, it will surely overheat.

I recommend the OEM T stat if you have the 4.7 unit. It runs $26 or so but is worth it.

Don