Originally Posted by Dave Sponaugle

Here it is, kinda long.

Engine cooling fan clutch test

The purpose of this procedure is to determine whether the fan clutch is functioning properly, or to determine if the clutch is not engaging, not disengaging, or causing vibration. Worn or damaged cooling fan clutches should be replaced with the proper service part. Do not attempt to modify the bi-metallic coil on the face of the fan clutch.
Locate a piece of cardboard large enough to cover the front of the radiator and an engine tachometer before proceeding with this diagnostic test.

1. Turn off air conditioner, heater - A/C fan, radio and any other accessories.

2. Before starting the engine, rotate the fan by hand. It should have some viscous drag, but it should turn smoothly during the full 360 degrees of rotation. The fan clutch should be replaced if it does not turn smoothly, or if it does not turn at all. If the fan clutch spins with no viscous drag when it is cold, and has not been run for an hour or more, it should be replaced.

3.To check for excessive fan clutch bearing clearance (cold fan clutch), hold the tip of the fan blade between the thumb and forefinger and lightly pull toward the radiator, then push toward the engine, repeating the motion several times. The total rocking movement at the end of the blade should be 5 mm (2/10") or less when no more than 8 ounces of force is applied. A force greater than eight ounces may deflect the blade and give erroneous results. Replace the fan clutch if more than 5 mm (2/10") of movement is observed.

4. Install a temporary engine tachometer if the vehicle is not equipped with a tachometer.

5. During the following tests, be sure to monitor the coolant temperature (temperature gauge in the instrument cluster) and shut off the engine if the temperature rises above the maximum recommended limit for the engine, or if coolant is discharged outside the system. The tests can be resumed using the following procedures after the coolant temp drops off to a normal operating level.

6. If the hood is left open, the fan noise may be easier to hear.

7. Start the engine. The fan clutch may be engaged when the engine is first started. This will be apparent from the noise level which has a distinctive roar. The fan clutch engagement is due to the viscous silicone fluid draining back and filling the gap between the input and output components. Running the engine at a consistent speed of about 2000 RPM should pump the fluid back to it's reservoir, disengaging the fan clutch after no more than five minutes. As the fan speed drops declines, the noise will drop off to a level inaudible to most observers. If the fan does not disengage after five minutes at 2000 RPM, the fan clutch should be replaced.

8. Stop the engine. Cut and install a piece of cardboard large enough to cover the front of the radiator with a 6" diameter hole in line with the fan clutch. If it is not possible to install the cardboard directly against the radiator, attach it to the A/C condenser.

9. Start the engine. With a gasoline engine at 2700 to 3000 RPM or a diesel at 2100 to 2300 RPM, the vehicle coolant temperature gauge will rise at a steadily as the engine warms, then appear to level off for a short time when the thermostat opens. Make a note of the temperature gauge position when the thermostat opens. The engine coolant temperature will continue to rise until the fan clutch engages.

10. Continue to observe the coolant temperature gauge. As the fan clutch engages the fan noise will continue to increase and then level off at full engagement. The fan may cycle off and on during the initial engagement. If the fan does not engage before the maximum safe operating temp is reached, it should be replaced.

11. After completion of the above tests, shut off the engine. Remove the cardboard cover from the front of the radiator. Restart and return the gas engine to 2700 to 3000 RPM or the diesel to 2100 to 2300 RPM, continuing to watch the coolant temperature which will begin to decrease. The fan RPM will drop to a reduced noise level where it was before the cycle began which indicates the fan clutch has disengaged. If the fan clutch remains engaged and the coolant temp has dropped below the thermostat opening temperature for at least five minutes, the fan clutch should be replaced.

12. If the fan clutch is replaced for any of the above test steps, the test should be repeated to verify the fix and owner satisfaction.

Originally Posted by IDIDieselJohn

I love my fan clutch, when that sucker locks in, it ROARS...like a Boss

Originally Posted by FORDF250HDXLT

just do me a favor,puller over good so i can zip up by ya.