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Discussion Starter · #1 ·
My wife drives a 2004 ZTW 2.3L duratec with about 140,000 miles. We had the car on a weekend trip to Seattle this summer with temps in the 80's. I noticed when we were in stop and go traffic for a long time that the temperature guage was very high (right up to the red). Obviously allowing the car to sit and idle wasn't helping, so I turned off the engine while sitting at a couple lights and the temperature returned to a normal range but quickly shot up to the high side again. Once I got on the highway, the temp maintained at a normal level, and we never noticed that problem again while on our trip. The car's coolant level was right where it should have been, and I could hear the fan kicking on periodically.

Today I noticed the same thing while driving in town, but it was about 40 F outside. I would suspect the thermostat, but there is one thing stopping me from diving in to remove it and test it right now. While we were in Seattle, the battery died on us and I had very little time and no tools with me, so I took the car to a little shop to have a new one put in. My question is this: Would the battery installation have possibly caused this problem by damaging a sensor wire or something?

Like I said, I don't drive this car often so I don't know if this has been happening the whole time (I sure hope not!). Does this just sound like a bad thermostat?

Thank you in advance for your advice.
 

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I would say you are correct it is the thermostat.
The only other thing it could be is the water pump, but those usually do not self repair.
The thermostat could easily get stuck, then unstuck, then stuck again.
So to do a 'not the mechanic $$ checkup' I would just dump in a new thermostat as 80% likely the solution.
It is cheap, pretty easy so it is what I would do.

And a bettery. no way would it have anything to do with the temps.
 

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The Radiator fans are the most common cause of this symptom, had an intermittent case myself at the Focus fest, BUT that was when doing repeated runs on the drag strip....

IF the "low speed" fan doesn't kick in when it should, the temp gets near the red line on the gauge B4 the high speed fans kick in to cool it down, causing a LOT of "angst" as you worry about overheating issues....

It's not that easy to test in "normal" operation, as they seldom kick on at all unless the A/C is engaged...

Even at idle in the drive, it may not get warm enough to kick on the low speed, much less the high speed!

Wire connections, relays & the resistor pack that allows low speed operation are the suspects - resistor pack on the 2.3 is harder to get to than on the other Foci, but the connector is somewhat accessible...

On mine, just unplugging the fan connections to check them cleaned 'em up enough to work fine for the last few months (since spring) when I FIRST wondered if I had an issue...

Luck!
 

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I'd guess it was the fans as well since the car only overheats while not moving when the fans would be doing their job. Check fan operation by turning the AC on, and seeing if the fan is running. Locations for the fuses and relays for the engine cooling fans are in the owner's manual. I'd check all of those before going for a more involved repair- although that's most likely where you'll end up. Fortunately Dtecs don't see the wiring damage that Zetecs do because the exhaust isn't right there behind the fans.
 

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Discussion Starter · #5 ·
My wife just got home from the store, so I popped the hood right away since I figured the engine would be plenty warm. I turned on the AC and noticed that both fans turn on and off together. I never noticed the fans running at different velocities. They seem to be turning fairly fast. Am I right in assuming that both fans work together and both have low and high? When should I see the fans running at a slower velocity? The temperature stayed within a normal range after letting it idle with the AC on for about 10 minutes.
 

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I think the slower velocity would kick in after letting it idle for a few minutes (depending on the outside temperature) with the AC and/or heater OFF. The fan motor will be powered through a different circuit that goes through the infamous fan resistor - the problem that I am having right now. If the resistor is shot, power couldn't go through that slow speed circuit. As the temp gauge get closer to the red line, the fan will be powered by the high-speed circuit and your fan will turn like crazy.
Yes, both fans run at the same speed. They are connected parallel.
 
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