Fan Clutch Diagnosis Noise
Fan noise may occur when the following normal conditions exist:
| • | The clutch is engaged for maximum cooling |
| • | The fan has been running for 15-60 seconds. |
| The clutch cannot redistribute the silicone fluid back to the normal disengaged operating condition (after overnight settling) for the first 15 seconds. |
Fan noise or an excessive roar may occur continuously when the following conditions exist:
| • | The engine is operating at a high speed. |
| A high speed is 2,500 RPM or more. |
| • | The clutch assembly locks up due to an internal failure. |
Replace the clutch if the following conditions exist:
| • | Rotating the fan by hand is impossible. |
| • | A rough grating feeling exists while turning the fan. |
Refer to Fan Replacement .
Fan Clutch Diagnosis Looseness
Inspect a loose fan assembly for wear. Replace the fan assembly as necessary.
A visible lateral movement at the tip of the fan blade under is visible at various temperature conditions. Approximately 6.5 mm (¼ in) maximum lateral movement, measured at the fan tip, is allowed. This movement is not cause for replacement.
Fan Clutch Diagnosis Silicone Fluid Leaks
The fan clutch operation is not affected by small fluid leaks which may occur around the bearing assembly. If the leakage appears excessive, replace the fan clutch.
Refer to Fan Replacement .
Fan Clutch Diagnosis Engine Oveheating
- Verify that the engine is cool. A cool engine will ensure complete disengagement of the fan clutch.
- Spin the clutch assembly by hand. The clutch assembly free-wheels if the assembly rotates more than five times.
- If the fan and the clutch assembly free-wheel with no drag, replace the clutch.
- If the clutch performs correctly with a slight drag, continue with the following procedure.
- Place a thermometer between the fan blades and the radiator.
- Insert the thermometer sensor through one of the existing holes in the fan shroud or place the thermometer between the radiator and the shroud.
- Cover the radiator grille in order to induce a high engine temperature.
- Start the engine.
- Turn on the air conditioning.
- Operate the engine at 2,000 RPM.
- Wait for 5-10 minutes for the clutch to engage.
- Replace the unit if the following conditions exist:
- As soon as the clutch engages, complete the following steps in order to assist in engine cooling:
- Verify that the fan clutch disengages after several minutes.
- Replace the fan clutch if the fan clutch fails to operate as described above.
Notice: Check for adequate clearance between the fan blades and the thermometer sensor before starting the engine, as damage could occur.
On some models, you may have to drill a 5 mm (3/16 in) hole in the fan shroud in order to insert the thermometer.
Observe the thermometer reading when the clutch engages.
The following conditions indicate fan clutch engagement:
| • | An increase or roar in the fan noise |
| • | A drop of 3-10°C (5-15°F) in the thermometer reading |
Important: Do not continue the test past a thermometer reading of 88°C (190°F). This action will prevent engine overheating.
| • | The clutch does not engage between 65-90°C (150-195°F). |
| • | Ensure that the fan clutch was disengaged at the start of the test. |
| • | No sharp increase in noise or no temperature drop was evident. |
| • | The fan noise level remained constantly high from the start of the test to 88°C (190°F). |
| • | Remove the radiator grille cover. |
| • | Turn off the air conditioning. |
| • | Run the engine at approximately 1,500 RPM. |
A reduction in fan speed and roar indicates disengagement.
