Fan Clutch Diagnosis
FAN NOISEFan noise is sometimes evident under the following conditions:
^ When the clutch is engaged for maximum cooling.
^ During the first 15 seconds to one minute after start-up until the clutch can redistribute the silicone fluid back to the fluids normal disengaged operating condition (after overnight settling).
Fan noise, or an excessive roar, generally occurs continuously under all high engine speed conditions (2500 RPM and up) if the clutch assembly is locked up because of an internal failure. If the fan cannot be rotated by hand, or if there is a rough grating feel as the fan is turned, replace the clutch.
LOOSENESS
Check a loose fan clutch assembly for wear. Replace the fan clutch as necessary.
Under various temperature conditions, a lateral movement is visible at the tip of the fan blade. About 6.5 mm (1/4 inch) maximum lateral movement, measured at the fan tip, is allowable. Replacement of the fan clutch is not necessary.
Make sure that the fan blade is installed properly. If the fan is installed incorrectly, it will cause an overheating problem.
SILICONE FLUID LEAKS
Small fluid leaks, occurring in the area around the bearing assembly, do not affect the operation of the fan blade clutch.
If leakage appears excessive, replace the fan blade clutch.
ENGINE OVERHEATING
1. In order to ensure complete fan blade clutch disengagement, begin testing with a cool engine.
2. If the fan blade clutch assembly free wheels with no drag, (revolves more than 5 times when spun by hand), replace the fan blade clutch. If the clutch performs properly with a slight drag, refer to step 3. Testing a fan blade clutch by holding the small hub with one hand, and rotating the aluminum housing in a clockwise/counterclockwise motion, causes the clutch to free wheel. Consider this operation normal and this test should not determine replacement.
3. Position a thermometer between the fan blades and the radiator. Do this by inserting the thermometer sensor through one of the existing holes in the fan shroud, or by placing the thermometer between the radiator and the fan shroud. On some models, you may have to drill a 5 mm (3/16 inch) hole in the fan shroud in order to insert the thermometer.
4. With the thermometer in position, do the following steps:
4.1. Sufficiently cover the radiator grille in order to induce a high engine temperature.
4.2. Start the engine.
4.3. Turn on the A/C.
4.4. Operate the engine at 2000 RPM.
IMPORTANT: Check for adequate clearance between the fan blades and the thermometer sensor before starting the engine.
5. Check the thermometer reading when the clutch engages. Allow about 5 to 10 minutes for the temperature to become high enough to engage 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 about 3-10°C (5-15°F).
^ If the clutch did not engage between 65-90°C (150-195°F), replace the assembly. Make sure that the fan blade clutch was disengaged at the beginning of the test.
^ If you observed no sharp increase in fan noise or temperature drop, and the fan noise level was constantly high from the start of the test to 88°C (190°F), replace the assembly. Do not continue this test past a thermometer reading of 88°C (190°F) in order to prevent engine overheating.
6. When the clutch engages, do the following steps:
6.1. Remove the radiator grille cover.
6.2. Turn off the A/C in order to assist in engine cooling.
6.3. Operate the engine at about 1500 RPM.
7. 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, replace the fan blade clutch.