Odd Focus cooling problem

Lately, I've been having a problem with the cooling system on my car that has both me and the dealer at a loss for an explanation.
The car is a 2001 (North American market) Focus ZTS. It has the 2.0L Zetec
engine and automatic transaxle. When I drive around town, the temperature gauge indicates that the car is running warmer than normal. (I used the dash's "test mode" to get an exact number: 112 deg C, where normal appears to be about 106C.) What's more worrisome to me is that when I take it out on the open road, and drive at highway speeds, the needle travels nearly all the way to the red zone, staying at 118 deg C. Once, it made it to the red zone (120C) but quickly dropped back down to 118C. Strangely, the car will lose a degree or two sitting at a light, but will warm up once back underway.
For the first seven years I drove it, the temperature needle never went past the halfway mark, so this behavior is pretty alarming. I took it to the dealer, and they did the following:
* Pressure test on the coolant system, and discovered a crack in the coolant recovery tank. Replaced tank, and the thermostat. That was a problem, but apparently not *the* problem, since it had no effect on the temperature. * Re-ran the pressure test. No leaks found. * Tested the engine block. No leaks there, either. (Thank goodness!) * Checked the coolant flow through the radiator. Situation normal. * Checked the thermostat again. Normal. * Checked the fan and associated relays. They seemed fine. (Actually, I could have told them that. I can hear the fan roaring at high speed after just about every highway trip.) * Checked the temperature sender and gauge. They also seemed to be working normally.
They spoke with Ford Engineering, which claimed that up to three-quarters of the gauge is normal (!), so they suggested they I drive it for a while, and let them know if the temperature went much higher than that.
So, does anyone know what the normal range of temperature is for this engine? I suspect 117-118C is too high. Perhaps more importantly, has anyone else here seen this problem?
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Benjamin Robinson snipped-for-privacy@freenet.tlh.fl.us
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* Checked the coolant flow through the radiator. Situation normal.
did you just check if there was flow or did you check if there was the proper amount of flow?

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In alt.autos.ford.focus, on the "Re: Odd Focus cooling problem" thread, qwerty wrote:

Well, I didn't check it personally; the dealer did. I'll ask him the next time I see him.
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Benjamin Robinson snipped-for-privacy@freenet.tlh.fl.us
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I was just wondering because the water pump has a plastic impellor that wears out and blades on it break = flow but not the proper amount

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