Cooling Fan Clutch

This procedure covers the removal and replacement of the cooling fan clutch on a 1970 AMC Rebel Machine with 390ci V8 engine.

Warnings

Tools required

Parts

• Fan clutch assembly × 1 — Use OEM specification or equivalent
• Fan shroud clips (if damaged) × 4 — Use OEM specification

Preparation

1. Ensure engine is completely cool to the touch
2. Disconnect negative battery cable to prevent accidental fan engagement
3. Position drain pan under radiator in case of coolant spillage
4. Remove upper radiator hose if additional clearance is needed
5. Document fan blade orientation and position for proper reassembly

Procedure

1. 1

   Remove fan shroud
   Remove the bolts securing the fan shroud to the radiator support. On the Rebel Machine, there are typically four bolts holding the shroud. Lift the shroud up and back slightly, but leave it resting on the fan - do not remove it completely yet. This provides access to the fan clutch while protecting the radiator.
2. 2

   Remove accessory drive belts
   Loosen the alternator adjustment bolt and pivot bolt to create slack in the belt system. Remove the drive belt(s) from the water pump pulley and fan clutch assembly. On 390ci engines, you may have one or two belts depending on accessories installed.
3. 3

   Position holding tool
   Hold the water pump pulley stationary using a water pump pulley holding tool, or carefully wedge a breaker bar between two pulley bolts and brace against the frame. The pulley must be prevented from rotating while loosening the fan clutch.
4. 4

   Loosen fan clutch nut
   Using the fan clutch wrench or 36mm open-end wrench, turn the fan clutch nut CLOCKWISE to loosen (reverse thread). The nut is located in the center of the fan clutch assembly where it threads onto the water pump shaft. Apply steady pressure - it may be tight from years of heat cycling. Once broken loose, continue turning clockwise until the clutch is free from the water pump shaft.
5. 5

   Remove fan and clutch assembly
   Carefully lift the fan blade and clutch assembly straight up and out of the engine compartment. Maneuver it past the radiator and shroud. Keep the assembly level to avoid spilling silicone fluid from inside the clutch if it has leaked internally. Set the assembly on a clean work surface with fan blades facing up.
6. 6

   Separate fan from clutch
   Remove the four bolts securing the fan blade assembly to the fan clutch. On AMC applications, these are typically 5/16 inch or 3/8 inch bolts. Keep these bolts as they will be reused with the new clutch. Inspect fan blades for cracks, bends, or damage and replace if necessary.
7. 7

   Clean mounting surfaces
   Clean the water pump shaft threads with a shop rag to remove any dirt, old silicone, or corrosion. Inspect the shaft for damage. Clean the back of the water pump pulley where the clutch seats. Any debris here can cause the clutch to sit improperly and fail prematurely.
8. 8

   Install fan blades to new clutch
   Attach the fan blade assembly to the new fan clutch using the original mounting bolts. Ensure the fan is oriented correctly - the curved side of the blades should face toward the radiator (pulling air through). Tighten bolts in a criss-cross pattern to ensure even seating. Hand-tight plus a quarter turn is sufficient.
9. 9

   Install new fan clutch assembly
   Carefully lower the fan and clutch assembly into position, threading the clutch onto the water pump shaft. Remember the reverse thread - turn COUNTERCLOCKWISE to tighten. Thread it on by hand as far as possible to ensure proper engagement and prevent cross-threading.
10. 10

    Tighten fan clutch
    Hold the water pump pulley stationary again with your holding tool. Using the fan clutch wrench, turn the clutch nut COUNTERCLOCKWISE to tighten. Tighten firmly - typically 30-40 ft-lbs equivalent by feel, as overtightening can damage the water pump bearings. The clutch should seat solidly against the pulley face.
11. 11

    Reinstall drive belts
    Route the accessory drive belt(s) back over the water pump pulley and other pulleys according to the original configuration. Adjust alternator position to achieve proper belt tension - approximately 1/2 inch deflection at the longest span. Tighten alternator mounting and adjustment bolts.
12. 12

    Reinstall fan shroud
    Position the fan shroud back into place, ensuring the fan blades are centered within the shroud opening with approximately equal clearance all around. Install and tighten the four shroud mounting bolts. Verify the fan blades do not contact the shroud at any point by manually rotating the fan through its full range.

Reassembly

1. Reconnect upper radiator hose if it was removed
2. Reconnect negative battery cable
3. Check coolant level and top off as needed
4. Ensure all tools and parts are removed from engine compartment

Verification

• Start engine and verify fan clutch engages properly as engine warms up
• Listen for unusual noises such as grinding, scraping, or wobbling that would indicate improper installation
• Check for coolant leaks around areas disturbed during the procedure
• Verify the fan clutch firms up and increases resistance as engine reaches operating temperature
• With engine at operating temperature, turn off engine and check that fan has significant drag when rotated by hand (should not spin freely more than 1-2 revolutions)
• Recheck belt tension after first heat cycle

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