My 94 civic has 160,000 miles on it. it started overheating last week. It doesn't go to oberheating immediately. I drove around a hour(mostly highway) and it did not over heat. I then drove 20 minutes city diving and it started overheating. I turned the heat on in the cabin and this helped the temperature go down. Temperature also goes down when there is no load put on the motor, for example when in gear the temp rises, shift to neutral and watch the gauge go down. I also noticed the coolant overflow tank was full to overflowing when the car gets up in the overheating range, when it cools down (the car is off for exteneded time) the coolant level goes back to normal in the overflow tank. It seems I have a pressure build up. I have replaced; the thermostat (and bled the system), cooling fan temp switch sensor (and bled the system), all fan relays under the hood, checked all fuses, it still overheats. There is no coolant in the oil and she doesn't blow white out of the exhaust. On a side note the fan switch for the blower motor stopped working a few weeks beofre this, so I do not have a working blowing fan in the car, not sure if there is any connection. I have people telling me the next option is the water pump? And if you do the water pump you add on the timing belt and tensioner pulley while you're in there. A pretty expensive suggestion.