I've got a 2001 Ford Focus that's been very reliable. Recently, though, while around-town local driving produces nothing out of the ordinary (engine temp gauge always at the same spot when warmed up, like it's glued in place), freeway trips produce an engine overheat (from its 1/2 normal position to as much as 3/4 but usually between the two) whenever I slow down to appx 35mph or stop at a light (again, after a freeway run). Speeding up to 40+ immediately causes the tempt to drop back to it's usual normal position. When I get home, the aux cooling fan is always running.
I've checked the front of the radiator and no blockage, fluid level is right where it should be.
So, what's going on here? All I can figure is maybe the thermostat is starting to stick and is unable to open fully for max coolant flow when needed.
Thoughts? Thx!...
Tomac

ETA: Turns out it was the radiator, new one installed today.

have enough coolant in it?  might have a small leak somewhere



might be a clogged radiator too with a car that old

Like you said start with the Tstat and go from there.

Check the T-stat, bet that will solve the problem.

Yup thermostat and new coolant. If it still doesnt seem quite right, I would look at replacing the radiator.
Also something else to think about (remote chance but possible), if its an automatic and the fluid is dark and smells burned, you could have an over heating transmission and that is causing the coolant temp to increase. That is if its an auto and it has an in radiator transmission cooler...