Edmunds Answers



  • sally38 06/15/08 8:58 am PST

    The cooling system on your honda requires all of the following components to work properly: 1) radiator; 2) electric fan that is attached to the radiator; 3) the thermostat; 4) the temperature sensor, which turns on the electric fan automatically when the coolant reaches to a certain temperature; and 5) the water pump, which is driven by the timing belt.
    The heater fan has little to do with the cooling system, so don't even bother with the heater controls at this point.
    Since the radiator is new, my first guess is that your thermostat is stuck in the "closed" position. The thermostat is a mechanical spring "thing" that opens at around 180 degrees F, and when it opens, the coolant around the engine block begins to flow through the radiator and becomes cooled, then the "cooled" coolant recirculates around the engine block, thereby removing the heat from the engine---it's a cyclical process. If the thermostat is stuck closed, then the coolant cannot flow through the radiator, or for that matter, the coolant doesn't flow at all, therefore, the engine WILL overheat.
    My second guess is that the electric fan or the temperature sensor is broken, or a fuse for the electric fan is blown. Honda's electric fans and sensor are alway very reliable, so look for a blown fuse before buying a new fan and/or sensor. If it is the electric fan or the temperature sensor, then the overheating problem would occur gradually. In other words, if it is a stuck thermostat, then then engine will overheat quite quickly.
    If everything else (1-4 above) works, then the last thing to check would be the water pump. In my many years of working on hondas, I've seen one frozen water pump, however, a frozen water pump cannot last long because it will cause the timing belt to fail. If the water pump cannot recirculate the coolant, then the engine will overheat. However, a frozen water pump should be a very very rare occurance.
    In summary, I suggest checking the thermostat first, to see if it is operating properly. Also, on your Honda, the temperature sensor is affixed to the housing covering the thermostat; therefore, you could check both the thermostat and the temperature sensor at the same time. The thermostat itself is quite cheap (maybe $10), but the labor to replace it is a different story. If you have some electrical experience with DC (12 volts), you could jump a wire from the battery to the electric fan to check if the fan is operating, or if you have a voltmeter, you could..., well I think I've written too much.
    Good luck with your overheating problem. An experienced Honda mechanic should be able to diagnose and solve the problem quite quickly IMHO.


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