Chrysler Repair: overheating, head gasket leak, chrysler concorde

Question
My '99 Chrysler concorde has started overheating after about 10 miles of driving; thermostat replaced, no change.  Radiator shop says it's not the radiator.  Any ideas?

Answer
Are the fans coming on when the temp rises toward the upper 1/3 of the gauge? If not, then the fan relay or fans may be bad. Are you loosing coolant? How many miles do you drive before having to add coolant, if you?  Have you felt the wheels to see if one might be hot due to a dragging brake.
Have you tried for a fault code readout of the controller. Autozone parts stores will often do that for free. Did the radiator shop test for exhaust gas in the cooling system, which is a sign of a head gasket leak? Do you get excessive white smoke when starting up the engine from cold which is also a sign of a head gasket leak?
Might there be air trapped in the cooling system? There is a valve on the filler pipe base that you can expell the air from if you attach a tube to it and open it while refilling the system after first draining off a couple of quarts and save for refill. When the level rises to the valve port then squeeze on the fat hoses to expel any air. Finally close the valve and fill the system the rest of the way.
Those are some ideas.
Roland