Fan Clutch: Testing and Inspection

Fig. 3 Bi-metallic coiled spring removal:

FAN DRIVE CLUTCH TEST

Do not operate the engine until the fan has been first checked for possible cracks and separations.

To check the clutch fan, disconnect the bi-metal spring and rotate 90° counterclockwise. This disables the temperature-controlled, freewheeling feature and the clutch performs like a conventional fan. If this cures the overheating condition, replace the clutch fan.

FAN CLUTCH NOISE
Fan clutch noise can sometimes be noticed when clutch is engaged for maximum cooling. Clutch noise is also noticeable within the first few minutes after starting engine while clutch is redistributing the silicone fluid back to its normal, disengaged operating condition after settling for long periods of time (over night). However, continuous fan noise or an excessive roar indicates the clutch assembly is locked-up due to internal failure. This condition can be checked by attempting to manually rotate fan. If fan cannot be rotated manually or there is a rough, abrasive feel as fan is rotated, the clutch should be replaced.

FAN LOOSENESS
Lateral movement can be observed at the fan blade tip under various temperature conditions because of the type bearing used. This movement should not exceed 1/4 inch (6.5mm) as measured at the fan tip. If this lateral movement does not exceed specifications, there is no cause for replacement.

CLUTCH FLUID LEAK
Small fluid leaks do not generally affect the operation of the unit. These leaks generally occur around the area of the bearing assembly, but if the leaks appear to be excessive, engine overheating may occur. Check for clutch and fan freewheeling by attempting to rotate fan and clutch assembly by hand five times. If no drag is felt, replace clutch.

FAN BLADE INSPECTION
Place fan on flat surface with leading edge facing down. If there is a clearance between fan blade touching surface and opposite blade of more than 0.090 inch (2mm), replace fan. (See caution at beginning of chapter.)