Chrysler Repair: cooling systems, upper radiator hose, accurate thermometer

Question
yes I have a 1198 concorde and the car has been overheating  i have change the fans the thermostat  the overheating only occurs when the cars is driven on the highwayalso there is no check engine light on the dashboard i was wondering if you have any ideas it will be appreciated. thank you  

Answer
Hi Wilmar,
Have you verified that you are truly overheating: do you get steam blowoff from the overflow bottle?
Have you tried to vent air from the upper radiator hose(there is a bleeder valve on the thermostat housing; attach a 1/4" hose to the nipple and direct it to a clean pan in front of the grill, then open the valve, then add coolant to the overflow bottle until there is flow out the hose. At that point stop adding fluid and begin to squeeze on the upper radiator hose so as to drive any air from the system that might be trapped there, then close the bleed valve and detach the 1/4" hose.)
Have you verified that the overheating (that you are detecting by the instrument panel gauge?) is actually a true excess temperature of the coolant? If you don't loose any coolant in the form of steam via the overflow bottle  then I would question whether you really have an overheat problem. Try checking the temp of the coolant while it is warming up to see what it reads when your gauge is mid-scale for example. It could be an inaccurate gauge sensor.
Also, are the cooling fans coming on in series as they are designed to do? The low speed fan is supposed to come on at 199F and then the high speed fan comes on at 230F. Let me know what the fans are doing as it relates to the gauge on the dash and to any reading you can make with an accurate thermometer.  
It may be that your radiator has some plugged tubes in it so that it cannot dissipate heat from the system. Have you flushed it with cooling system cleaner?
Those are my questions/suggestions.
Roland