It should have resistance when hot or super cold [hasnt been spinning]
It shouldnt free spin, im not however good at diagnosing fan clutch problems.

Does it happen when sitting in traffic only? this is a dead giveaway

 

Don't keep overheating it or you will kill that aluminum motor.

 

I bet it is a clogged radiator.....

Ask if someone near you has a infrared termometer or buy a cheap one and measure the temp in all the radiator. Actually, if you turn on the AC, the fans would help to push air in the radiator and will also help to cool it down.

another trick you can use to reduce the overheating at list for a few additional minutes while you are driving is to turn on the heat in your car. The heater uses the heat of the engine, and helps to keep it cool.

 

Let me ask a basic question: If you took the hoses loose, could you do a basic flush with a garden hose? Would that tell you anything?

 

Check your radiator. You can have it rodded out for about 75 dollars. Well worth it. Old radiators in these vehicles clog easily. If it is clogged flushing with a hose will do little. You need to have it rodded.