OVERHEATING ALL OF A SUDDEN H E L P

I have a 99 Explorer with the 4.0 V-6 motor. It has about 100k miles on it. Today, I stopped at a friends house about a block from my house (so it had not gotten to the normal operating temp.). I left it running, with
the A/C on, and after a matter of minutes the motor sped up. It did not sit more than 3 to 5 minutes idling with the A/C on. When I got into the Explorer it lacked about 1/4" from being to the red line. With the outside temp at about 100 degrees, I figured it would cool off after I drove a few blocks. WRONG The gauge never went any higher. I brought my Explorer back home, and after letting it cool off, I started to drive around the block. Same problem. I did turn the heater on full blast, and it brought the temp down. Any suggestions would be DEEPLY APPRECIATED Thanks, Barbara
Please feel free to e-mail ANY advise to:
snipped-for-privacy@comcast.ne
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@comcast.net says...

Sometimes the temp was OK other times it was near the top of the guage.
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It sounds like the fan isn't working. There is usually a thermostatic switch that turns it on. If this is the case, then your truck should be able to run without overheating on the highway. You should be able to get either the fan or the switch replaced.
It could also be a blocked radiator. Or not enough fluid in the radiator. So you should have the fluid checked when the engine is cold. (Note: never check the radiator fluid when the car is warm: Serious burns can result.)
I suspect that it is a bad switch, but you should make the fluid level and radiator are ok, too.
Jeff
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in alt.autos.ford,

Like others have said, check your water level, then when it's warm check the upper hose going from the motor to the rad, make sure it's hot when your gauge is showing hot. It could be a stuck thermostat.
~Brian
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Our's is a 2000 EB, the thermostat went bad and the system over heated. Ford replaced the thermostat and the thermostat housing. I'll bet the thermostat broke.
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