I have 2003 Dodge Grand Caravan 3.3L and it overheats while driving over 40mph but when I drive below 35 and stop a lot it keeps the temperature at normal level. Radiator fan works just fine and antifreeze at normal level (no leaks). Is it thermostat or radiator cap going bad?

 

could be water pump, radiator, air restriction through radiator or, maybe thermostat, i really doubt it's the cap. I've left mine off accidentally and never had an overheating problem

I came across a posting where someone had the same problem where the water pump impeller was slipping on the shaft at high rpm

i saw another where the raditor cores were plugged and at higher engine load more heat and the radiator couldn't keep up with cooling

 

Radiator I've changed 6 month ago to aftermarket radiator. I really doubt if radiator is a problem. Also I'm getting good hot air from a heater. I just don't know what to replace first.

 

did you replace the radiator because of the overheating problem? i read about a new radiator causing transmission failures. point being you just can't assume a new part is a good part

 

Check the thermostat, if it fell apart the coolant flows too fast for the radiator to remove the heat.

 

idk about that. race cars dont use a thermostat and don't overheat but if the stat is sticking or not opening fully, it could be causing overheating but i'm really not thinking this is the problem.

maybe instead of the approximation gauge, they should have a look at what the real temp is. i'd use a quality scanner, look at the pcm data and see what the exact temp is showing to the computer

 

ya, I guess I wouldn't know.

 

My dodge Dakota and eagle talon both were over heating at highway speeds but not at slower speeds, my talon it fixed it, but my Dakota it was the radiator that was clogged
was the thermostat replaced with the radiator?
if not the thermostat is a cheep part and a fairly quick fix