How do you check to see if the fan clutch is working properly??

 

When you spin the fan by hand ( with the engine off but warm or cold ) it should turn just a few inches, if it turns more than about a 1/4 of a turn then it is getting wore out, if it turns 1/2 way around then it is bad or if you see oil leaking from it its about time to replace it. Another way is when you start the car in the morning you should hear the fan pulling strong then in a few seconds the noise should slowly stop this indicates the fan is working properly

 

If it's only overheating at idle and low speed, but cools down if you speed up, then it's almost definitely the fan clutch.