GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 STS 🢒 Body 🢒 Wiring Systems 🢒 Fan Clutch Diagnosis

Step

Action

Yes

No

DEFINITION: Testing the engagement and disengagement of the fan clutch.

1

Were you sent here from Symptoms or another diagnostic table?

Go to Step 2

Go to Symptoms - Engine Cooling

2

Is there excessive fan air noise?

Go to Step 3

Go to Step 4

3

Fan air noise is normal during cold engine start up.

Does the fan noise go away at normal engine operating temperature?

Go to Step 13

Go to Step 4

4

Important: The engine must be turned OFF and the engine temperature should be cold.

Rotate the fan clutch.

Does the fan clutch rotate?

Go to Step 5

Go to Step 14

5

Visually inspect the fan blades for cracks, looseness or damage.

Are the fan blades in good condition?

Go to Step 6

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.
    • Excess leakage will prevent the fan clutch from engaging.

Is the silicone fluid leakage excessive?

Go to Step 14

Go to Step 7

7

Inspect the fan clutch for proper installation.

  1. Move the fan blade back and forth in a lateral motion.
  2. Inspect for fan blade to fan clutch movement.

Is the fan blade loose at the fan clutch?

Go to Step 10

Go to Step  8

8

Inspect the fan clutch for wear.

  1. Move the fan blade back and forth in a lateral motion.

    2. Important: Approximately 6.5 mm (¼ in) movement at the tip of the fan blade is normal.

  2. Inspect for fan clutch lateral movement.

Is the fan clutch lateral movement excessive?

Go to Step 14

Go to Step 9

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?

Go to Step 11

Go to Step 14

10

Tighten the fan. Refer to Fastener Tightening Specifications .

Is the repair complete?

Go to Step 15

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11

Perform a fan clutch engagement test.

  1. Ensure the engine coolant level is full.
  2. Ensure the cooling fan drive belt tension is correct and not slipping.
  3. Position and secure a thermometer between the fan clutch and the radiator.
  4. Ensure the cooling fan is disengaged before starting this test.
  5. Sufficiently cover the radiator grille to restrict the air flow.

    6. Important: Do not allow engine temperature to exceed 121°C (250°F).

  6. Start the engine.
  7. Turn the A/C ON.
  8. Operate the engine at approximately 2,000 RPM.
  9. Inspect the thermometer reading when the fan clutch engages.
  10. Do not continue this test if the fan clutch does not engage between 85-96°C (185-205°F).

Fan clutch engagement will be indicated by an increase in fan air noise, fan speed, and a drop of about 3-10°C (5-15°F) on the thermometer reading.

Did the fan clutch engage between 85-96°C (185-205°F)?

Go to Step 12

Go to Step 14

12

Once the fan clutch engages, perform the following steps:

  1. Uncover the radiator grille.
  2. Turn the A/C OFF.
  3. Operate the engine at approximately 2,500 RPM to reduce the engine operating temperature.
  4. Remove the thermometer.

Did the engine return to normal operating temperature?

Go to Step 13

--

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?

Go to Step 15

Go to Step 14

14

Replace the fan assembly. Refer to Fan Replacement .

Is the repair complete?

Go to Step 15

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15

Operate the fan clutch to verify proper operation.

Did you find and correct the condition?

System OK

Go to Step 2