K 1500 Truck 4WD V6-4.3L VIN W (1997)
Fan Clutch: Testing and Inspection
Engine Overheating
WARNING: To help avoid personal injury or damage to the vehicle, a bent, cracked, or damaged fan blade should always be replaced.
A. Start with a cool engine to ensure complete fan blade clutch disengagement.
B. If the fan and clutch assembly free-wheels with no drag (revolves more than five times when spun by hand), replace the clutch. If the clutch
performs properly with a slight drag, go to step C.
^
Testing a fan blade clutch by holding the small hub with one hand and rotating the aluminum housing in a clockwise/counterclockwise motion
will cause the clutch to free-wheel, which is a normal condition when operated in this manner. This should not be considered a test by which
replacement is determined.
C. Position a thermometer so it is located between the fan blades and the radiator. This can be achieved by inserting the thermometer sensor through
one of the existing holes in the fan shroud or by placing it between the radiator and the shroud. On some models, it may be necessary to drill a 5
mm (3/16 inch) hole in the fan shroud to insert the thermometer.
D. With the thermometer in position, cover the radiator grille sufficiently to induce a high engine temperature, start the engine, turn air conditioning
on, and operate at 2000 RPM.
E. Observe thermometer reading when the clutch engages. It will take approximately 5 to 10 minutes for the temperature to become high enough to
allow engagement of the fan blade clutch. This will be indicated by an increase or roar in fan air noise and by a drop in the thermometer reading of
approximately 3°C to 10°C (5°F to 15°F).
^
If the clutch did not engage between 65°C to 90°C (150°F to 205°F) the unit should be replaced. Be sure the fan blade clutch was disengaged
at the beginning of the test. Do not continue the test past a thermometer reading of 90°C (205°F) to prevent engine overheating.
F. As soon as the clutch engages, remove the radiator grille cover and turn the air conditioning off to assist in cooling system. Run the engine at
approximately 1500 RPM.
G. After several minutes, the fan blade clutch should disengage as indicated by a reduction in fan speed and roar. If the fan blade clutch fails to
function as described, it should be replaced.
