My durango started to run cool ...temp gauge shows around 170 or so. Replaced thermostat twice now using 195's ... to no avail and still cool.
Replaced radiator cap with new one ...no water temp change.

After warm up (as little as it is) I can take the radiator cap loose slowly can hear water pass back into the reservoir .... remove cap without water spewing out ... not hot ..just warm.
Top radiator hose gets hot if holding it tight, but lower is pretty cool. Air at heater vents will get warmer as engine speed increases and cool as fast went letting off throttle ...
engine is 5.2 with 50,000 miles on it. cardboard in front of the trans cooler does not seem to make much difference. clutch fan is free and will spin by hand when the engine is off.
I have been told that a intake manifold gasket or a head gasket may make it act in this manner ... any suggestions where else to look ?