Dear Tom and Ray:

I have a 1993 Escort LX hatchback that runs hot when sitting in slow
traffic or at an extended stoplight. It has never overheated, but merely
moves into the high range. As soon as I return to highway driving, it drops
back down below the halfway point. It usually heats up when I have to creep
along on the highway or on an off-ramp. I live in the Deep South, and I'm
worried about it overheating in the noonday sun. Is my thermostat shot? My
water pump? Is this normal? I'm an historian with a history of automotive
cluelessness. Help! -- Dan

TOM: You may not know this, Dan, but my brother is an historian, too. In
fact, his college thesis was "Unexplained Cheap Car Temperature Variations
in late 20th Century America: A Social, Historical, and Metaphysical
Analysis."

RAY: From a historical perspective, I'd be inclined to look at the fan,
Dan. The problem seems to happen when you slow down after highway driving.
And that's when you've built up the greatest amount of heat in the engine,
but have no natural breeze blowing through the radiator.

TOM: When you're driving at highway speed, you're creating a "natural" fan,
and the engine runs at its normal temperature.

RAY: So checking the archives, I come across two similar situations. One
took place up North, on June 4, 1996. It was documented by historian Doris
Kearns Goodwrench in her now famous book "Ford Escorts: What Crap." This
particular overheating problem is known as the "1996 short-cycling
incident."

TOM: When a fan is short cycling, it's not staying on long enough to
properly cool the engine. The cause tends to be a bad coolant temperature
sensor, which is what signals the fan to come on and off. So you might have
your mechanic try replacing the CTS. It's cheap.

RAY: The other famous case was documented by a famous Southern historian,
Shelby Foote-Pedal, in 1995. A man was having a similar overheating
problem, and his mechanic finally discovered that his fan motor was dying
and the fan was turning too slowly. This would create a similar situation,
where you'd be fine at highway speed when the fan was unnecessary, but
you'd run hot when you need the full force of the fan to cool the engine.

TOM: That's more rare, Dan, but if a new coolant temperature sensor doesn't
fix it, at least ask your mechanic to check the fan speed. And if he
doesn't believe your story, tell him to write to us and we'll send him the
complete bibliography.