Fan Clutch: Testing and Inspection

Do not operate the engine until the fan has been first checked for possible cracks and separations.
Run engine at a fast idle speed (1000 RPM) until normal operating temperature is reached. This process can be done more quickly by blocking off the front of the radiator with cardboard. Regardless of temperatures, unit must be operated for at least five minutes immediately before being tested.
Stop engine and using a glove or a cloth to protect the hand, immediately check the effort required to turn the fan. If considerable effort is required, it can be assumed that coupling is operating satisfactorily. If very little effort is required to turn the fan, it is an indication that the coupling is not operating properly and should be replaced.

Bi-Metallic Coiled Spring Removal:

The clutch fan may be tested while vehicle is being driven. To check, disconnect the bimetal spring, Fig. 2, and rotate 90° counterclockwise. This disables the temperature-controlled, free-wheeling feature and the clutch performs like a conventional fan. If this cures the overheating condition, replace the clutch fan.