Radiator Cooling Fan Fan Clutch Testing and Inspection (Express 2500 2WD V8-48L VIN V)
Fan Clutch: Testing and Inspection
Fan Clutch Diagnosis
Noise
Fan noise is sometimes evident when the following normal conditions exist:
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The clutch is engaged for maximum cooling.
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The engine has been running for 15-60 seconds after start-up. After this time, the clutch can redistribute the silicone fluid back to the normal
disengaged operating conditions.
Fan noise or an excessive roar may occur when the following conditions exist:
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The engine speed is 2,500 RPM or higher.
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The clutch assembly is locked up due to an internal failure.
Rotate the fan (1).
With the engine off, replace the clutch (2) if the following conditions exist:
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The fan cannot be rotated by hand.
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The fan produces a rough, grating feel as it turns.
Looseness
If the fan assembly is loose, inspect the fan assembly for wear. Replace the fan assembly as necessary.
Observe the tip of the fan blade for lateral movement. Lateral movement occurs under various temperature conditions. A lateral movement measuring
6.5 mm (¼ in) is normal. This amount of movement is not cause for replacement of the assembly.
Silicone Fluid Leaks
Small fluid leaks that are present around the bearing assembly do not affect the fan clutch operation. If leakage appears extensive, replace the fan
clutch.
Engine Overheating
Notice: Check for adequate clearance between the fan blades and the thermometer sensor before starting the engine, as damage could occur.
Use the following procedure in order to diagnose the causes of engine overheating:
1. Ensure that the engine is cool. This will allow complete disengagement of the fan clutch.
2. Important: Testing the fan clutch by rotating the fan in a repeated clockwise/counterclockwise motion causes the clutch to free-wheel.
Free-wheeling is a normal result of rotating the fan in this manner. Conduct further tests in order to determine if it is necessary to replace the fan
clutch.
Spin the fan and clutch assembly by hand. If the fan and clutch assembly easily revolves more than 5 times with no drag, replace the fan clutch.
3. If the fan clutch performs correctly but exhibits drag, position a thermometer between the fan blades and the radiator. Use any of the following
methods in order to position the thermometer:
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Insert the thermometer sensor through one of the existing holes in the fan shroud.
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Place the thermometer between the radiator and the shroud.
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On models that do not have holes in the fan shroud, drill a 5 mm (3/16 in) hole in the fan shroud. Insert the thermometer in the hole.
