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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 596 (Engine Cooling System) >> Diagnostic Information and Procedures >> Fan Clutch Diagnosis >> Engine Overheating

Engine Overheating

WARNING: This page is about a different car, the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, and 2002 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
  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 clutch. Refer to Fan Clutch Replacement . If the clutch performs properly with a slight drag, refer to step 3. Testing a fan blade clutch by holding the small hub with 1 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. Perform the following steps:
    1. Sufficiently cover the radiator grille in order to induce a high engine temperature.
    2. Start the engine.
    3. Turn on the air conditioning (A/C) if equipped.
    4. Operate the engine at 2000 RPM.
  4. Inspect the coolant temperature when the clutch engages. Allow about 5 to 10 minutes for the temperature to become high enough in order 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 coolant temperature reading of about 3-10°C (5-15°F).
    • If the clutch did not engage between 110-121°C (230-250°F), replace the assembly. Ensure that the fan blade clutch was disengaged at the beginning of the test.
    • If you did not observe a sharp increase in the fan noise or a temperature drop, and the fan noise level was constantly high from the start of the test, replace the assembly. Do not continue this test past a thermometer reading of 121°C (250°F) in order to prevent engine overheating.
  5. When the clutch engages, do the following steps:
    1. Remove the radiator grille cover.
    2. Turn off the A/C in order to assist in engine cooling.
    3. Operate the engine at about 2500 RPM.
  6. 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. Refer to Fan Clutch Replacement .
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