Fan clutch failure?

Fellows,

I have a 1995 Dodge van with a V6 Magnum engine. I have checked a number of posts in this section, but I am unsure what my problem could be, but I suspect the fan clutch. I replaced the water pump last autumn.

The temperature remains in normal range (normal for the entire time I have owned it since new) at idle and at 30 m.p.h.

When driving on the freeway at 65 m.p.h., the temperature gauge climbs to 3/4 hot.

As soon as I reduce speed back to 30 m.p.h., the temperature drops back to within normal range.

This has been going on for a couple of weeks. I just purchased a new radiator cap and thermostat, but as I think of it, the symptoms do not seem to indicate a thermostat or pressure cap problem. I am drifting to thinking that the fan might be blocking air flow at highway speed.

Any ideas?

P.S. I have not yet actually replaced the thermostat or cap.