you say you checked the coolant temp. sensor(?) is that the one with the one wire to it that tells the dash board guage that the temp. is high or low(NORMAL)????? if so then you also have to check the other sensor(ECT ) that has TWO wire attached to it.. this is what goes back to the computer to tell the computer when to turn the fan on....
the coolant temp. sensor that has one wire to it only goes to the dash to report on the heat of the coolant to the guage....