You have one of the 2 problems listed above, but the two will overheat under completely different circumstances.
A cooling fan problem will not be noticeable while you're moving on the highway or at a decent speed. As soon as you slow down or come to a stop, it will overheat.
A thermostat will overheat regardless of where you're driving, and will overheat quicker if the engine is turning faster like on the highway.
Test the cooling fan by idling the engine until it starts to overheat. If the fan's don't come on, then you have cooling fan problems. You can also visually inspect the wiring going to the engine cooling fans. What happens on Zetec engines is that the heat from the exhaust manifold melts the cooling fan resistor and power plug. A new plug can be purchased from the Ford dealer, as well as a fan resistor, if needed. I'm guessing your problem is the plug because if it was just the resistor, the fan would come on high speed.
There is a way to watch the thermostat temperature to see if it is actually working. With the key OFF, press and hold the odometer reset button. Continue to hold, and turn the key to ON. Wait until the gauge needles start jumping around before you release the odo reset button. The odo display should read [test]. Now every time you press and release the reset button you will scroll through one of 30 test modes. Look for the one where the odo will read [15 C] or whatever temperature in C that it should be at the time. If you accidentally scroll past it, then just circle around again, until you turn the key off the odometer will stay in test mode. Now start the engine, and watch as the temperature climbs. If the thermostat is working, it will climb to around 95C then cool off, and rise up again. If it is not working, then it will continue to climb, and the engine will overheat.
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Originally Posted by the user formerly known as ZX3_Chick
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