My 99 Durango will heat up to 210 and then act like it is starving for fuel. I have replaced thermostat, flushed radiator, cleaned fins, checked clutch fan. It also takes two turns of the key before starting to prime the fuel. The truck runs fine until the heat climbs.

 

Maybe try a 180 degree thermostat if you haven't yet and check your fuel pressure, the pump may be going bad.

 

We have replaced the thermostsat with a lower temp model. The fuel pressure is good.

 

O2 sensor maybe?

 

Change your trans filter and fluid. Not just a flush. Also have your catalatic converter checked for back pressure. You should have no more than 5 lbs back pressure. Most shops will do this for free.

 

Your radiator could be clogged up. Even with flushing it may not help. This happened to my Nissan Maxima couple months ago. It started overheat and I changed everything short of the water pump and radiator. After my mechanic did some testing on the pump, the pump is working fine but we found out the radiator was not flowing fluids very well and then found the lower half of the radiator was clogged. So replaced the radiator and been good ever since. This radiator was the OEM radiator on my 92 maxima and has over 150k on the radiator so I guess it was time to get it replaced anyways.

Also, when your Durango reaches 210 degrees, the PCM will try to put your Durango in conservative or limp mode to try to save your motor. the motor will act like it lost half of its available power. This is a big sign to warn the driver to address the overheating issue before you end up rebuilding/replacing the motor. Once your D cools down below 210, it will run normally again.