I drive a 99 dodge Durango aka “moose” and I live in Louisiana. Last year I replaced the water pump, and last week a mechanic put in a new thermostat. Moose had been overheating and had only been getting 5.5 mpg. Since the new thermostat, moose is getting the correct mpg at 14.9 mpg-- odometer and DTE screen match. Moose is still overheating on the way home from work in the afternoons though. We are hitting 100plus temps here now, with the humidity. Afternoons are scorchers!! Temp gauge is going up 3 quarters and higher. So, I am driving the interstate at 60-70 mph with the heater turned on full blast! Radiator is full 50/50. I am running a quart low on oil. All the other fluids are correct. When I drive moose at night, temp gauge stays right at 210 at the halfway mark and doesn’t go up. It’s the heat of the day that is jacking up the temp after about a half hour on the road and about 30 miles of driving one way. So what’s up with that, huh? How do I cool moose down in the afternoons? I could use a sprinkler system in the driver’s seat too! Reminds me of when I drove across the desert in a Peuogeot that was overheating. I drove in the slow lane with the heat up full blast then too. then I just parked on the side of the road when the peugeot overheated. there was nobody around but me and the tumbleweed and the most beautiful panoramic views you might ever see. I drove halfway across the country! I later blew a hole in the engine block of that vehicle because of a broken thermostat! Oh yeah!! Bad Karma?
Look at the front of the radiator/condensor for debris buildup of bugs and such. If it appears there’s no restriction in that area, then the problem might be with a partially restricted radiator.
Tester
First, try CLEANING the radiator and A/C condenser from behind with a pressure washer. I bet they are packed full of BUGS!! If necessary, REMOVE them to clean them thoroughly, but you should be able to get in there somehow.
If that doesn’t work, REPLACE the radiator and while it’s out, clean out that A/C condenser…
On a truck this age, check , CLEAN, or correct flows.
Radiator internal flow.
Air flow through fins of radiator, a/c condenser, trans cooler. clean debris from fins straighten as needed.
Air flow around the engine and area. Clean the engine of grease/dirt build up, it acts as an insulating blanket on the engine.
Air flow problem suspected. I took the bra off the bottom of the front end to check the cooling system for leaks. I never put it back on! Eureka!! When I grow up, I want to be just like you!!! I will let you know what happens after I do this. Thanks!!