I have a 2003 Dakota 3.9. In the winter the heat and temp are fine. Now that it is getting warmer, 60-70degs, the radiator temp is going up. There is no rough idle. The fluids remain the same. I changed the t-stat to 185. Bled the system numerous times. Still runs hot. Not sure of the temp except that it shows higher on the idiot gauge than normal. Where is the sensor for the electric fan? The fan comes on when the CA is turned on, but doesn't seem to come on when really hot. I blocked the radiator from air and got it hot. No electric fan. Is the Radiator next.......

 

The efan or electric fan is usually only for overheat conditions and when using the AC. Your main cooling is from the mechanical fan sounds like you dont have one it must have been removed by the previous owner for a few extra HP.

This is the fan Im talking about or part of it below is the fan blade.

http://www.rockauto.com/en/moreinfo....413009&jsn=439

This is attached to it and is your main cooling fan

http://www.rockauto.com/en/moreinfo....413009&jsn=450

This is what it should look like Dakota Durango same engine

 

Thanks DakAZ. I still have the original fan. I blocked my radiator to put it into overheat mode. I don't know if I reached that or not. the electric fan never came on. I can't tell what the actual temp is with the idiot gauge in the truck. I still wonder if the sensor that turns on the fan for overheat is good. I was wondering where that is and how to check it. the truck seems to heat up real fast and stays higher temp than winter now that it is warmer. it doesn't overheat, it just gets hotter and the truck then develops engine codes when it gets hot. am I still leaning towards radiator? The flow in the cap area is flowing but I don't know how much is good flow. wish I could see into the radiator to see the tube openings.

 

The cooling fan is controlled by the PCM. Like 98 says though, the mechanical fan is the primary fan for cooling. The electric is really to assist with the a/c.

Are you actually getting hot? Replace the sending unit in the intake manifold. What codes are you getting?

A good radiator shop can flow test the core.