[Beergeek]

I have searched the forum, and read a few of the posts. But I think my symtoms are a little different:

I tend to overheat faster at highway speeds. The faster I go, the faster/more I overheat. I don't have the problem driving city streets, stop/go traffic.

I have flushed the radiator twice. Seems to have helped a little, but maybe it was just a cooler day.

I changed the water pump at 160K, and currently I'm at 190K. The old water pump looked fine.

I took the thermostat out a month ago. Doesn't seem to matter.

I think (I hope) it's down to the fan clutch or the radiator. I saw one diagnostic in here for the radiator I haven't tried: Start up cold, run a few minutes, shut the motor down, then feel the radiator to see if there is a temperature gradient, indicating a plugged radiator (it seems to flow fine when flushing).

Is there a good diagnostic for the fan clutch?