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Test B: Fan Clutch Diagnosis

WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
  1. If the Engine Cooling Diagnostic System Check was performed, go to next step. If the Engine Cooling Diagnostic System Check was not performed, go to DIAGNOSTIC SYSTEM CHECK - ENGINE COOLING  under SELF-DIAGNOSTIC SYSTEM.
  2. Is there excessive fan air noise? If so, go to next step. If not, go to TEST A: EXCESSIVE FAN NOISE  .
  3. Fan air noise is normal during cold engine start up. Does the fan noise go away at normal engine operating temperature? If so, go to step  13 . If not, go to TEST A: EXCESSIVE FAN NOISE  .
  4. The engine must be turned off and the engine temperature should be cold. Rotate the fan clutch. Does the fan clutch rotate? If so, go to next step. If not, go to step  14 .
  5. Visually inspect the fan blades for cracks, looseness or damage. Are the fan blades in good condition? If so, go to next step. If not, go to step  15 .
  6. Visually inspect the fan clutch for signs of silicone leakage. Slight silicone leakage may not effect the fan clutch engagement. Excessive leakage will prevent the fan clutch from engaging. Is the silicone fluid leakage excessive? If so, go to step  14 . If not, go to next step.
  7. Inspect the fan clutch for proper installation. Move the fan blade back and forth in a lateral motion. Inspect for fan blade-to-fan clutch movement. Is the fan blade loose at the fan clutch? If so, go to step  10 . If not, go to next step.
  8. Inspect the fan clutch for wear. Move the fan blade back and forth in a lateral motion. Approximately 6.5 mm (1/4 in) movement at the tip of the fan blade is normal. Inspect for fan clutch lateral movement. Is the fan clutch lateral movement excessive? If so, go to step  14 . If not, go to next step.
  9. The fan clutch should have more turning resistance when the engine is at or above normal operating temperature. Does the fan clutch have more resistance when the engine temperature is raised? If so, go to step  11 . If not, go to step  14 .
  10. Tighten the fan. Is the action complete? If so, go to step  16 .
    11. CAUTION: Do not allow engine temperature to exceed 250°F (121°C).
  11. Perform a fan clutch engagement test. Ensure the engine coolant level is full. Ensure the cooling fan drive belt tension is correct and not slipping. Position and secure a thermometer between the fan clutch and the radiator. Ensure the cooling fan is disengaged before starting this test. Sufficiently cover the radiator grille to restrict the air flow. Start the engine. Turn the A/C ON, if equipped. Operate the engine at approximately 2000 RPM. Inspect the thermometer reading when the fan clutch engages. Do not continue this test if the fan clutch does not engage between 185-205°F (85-96°C). Fan clutch engagement will be indicated by an increase in fan air noise, fan speed, and a drop of about 5-15°F (3-10°C) on the thermometer reading. Did the fan clutch engage between 185-205°F (85-96°C)? If so, go to next step. If not, go to step  14 .
  12. Once the fan clutch engages, uncover the radiator grille. Turn the A/C OFF, if equipped. Operate the engine at approximately 2500 RPM to reduce the engine operating temperature. Remove the thermometer. Did the engine return to normal operating temperature? If so, go to next step.
  13. As the engine temperature returns to normal, the fan clutch will disengage, indicated by a reduction in fan air noise and fan speed. Did the fan clutch disengage? If so, go to step  16 . If not, go to next step.
  14. Replace the fan clutch. See FAN CLUTCH  under REMOVAL & INSTALLATION. Is the repair complete? If so, go to step  16 .
  15. Replace the fan blades. See COOLING FAN & SHROUD  under REMOVAL & INSTALLATION. Is the repair complete? If so, go to next step.
  16. Operate the fan clutch to verify proper operation. Did you find and correct the condition? If yes, system is OK. If not, go to step  2 .
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