Here's a general procedure. Specifics may vary slightly depending on your exact engine (4.3L V6 or the less common 2.9L V6). Always consult a repair manual specific to your vehicle's year and engine for detailed diagrams and torque specifications.
Tools You'll Likely Need:
* Socket wrench set: Including the correct size socket for the fan clutch nut (usually a large one).
* Wrench: Possibly a box-end or open-end wrench to hold the water pump pulley while you loosen the fan clutch nut. A pulley holder tool is ideal but not always necessary.
* Penetrating oil (like PB Blaster): Apply this to the fan clutch nut several hours or overnight before attempting removal to help break loose any corrosion.
* Gloves: To protect your hands from hot coolant and sharp edges.
* Jack and jack stands (highly recommended): For safer access and stability.
* Drain pan: To catch any spilled coolant.
* Shop rags: For cleaning up spills.
Procedure:
1. Drain the coolant: Locate the coolant drain petcock at the bottom of the radiator. Place your drain pan underneath and carefully open the petcock to drain the coolant.
2. Remove the serpentine belt: This usually involves loosening the tensioner pulley. Consult your repair manual for the proper procedure; it varies between different years and engine types.
3. Access the Fan Clutch: You'll need to get to the fan clutch which is mounted on the water pump pulley. This may involve removing other components, depending on your Astro's configuration. You may need to remove the shroud surrounding the fan and radiator for better access.
4. Remove the Fan Clutch Nut: This is the most challenging part. The nut is typically very large and can be extremely tight due to corrosion. Use the penetrating oil beforehand. Hold the water pump pulley firmly while loosening the nut. A wrench on the pulley itself, a pulley holder tool, or even a helper holding it steady is highly recommended to prevent the pulley from turning. Turn the nut counter-clockwise to loosen.
5. Remove the Fan Clutch: Once the nut is removed, the fan clutch should be able to be pulled off the water pump pulley. It might be stubborn; gently wiggle it and tap it lightly if needed. Avoid damaging the water pump pulley or the fan itself.
6. Clean and Inspect: Clean any corrosion or debris from the water pump pulley. Inspect the water pump for any damage.
7. Reassembly (When Installing a New Clutch): The installation process is essentially the reverse of removal. Remember to torque the nut to the manufacturer's specified torque value (found in your repair manual).
Important Considerations:
* Seized Nut: If the nut is severely seized, you might need to use a breaker bar or an impact wrench. Be extremely careful not to damage the water pump pulley.
* Professional Help: If you're uncomfortable with any of these steps, take your vehicle to a qualified mechanic. Incorrect removal can damage the water pump or other components.
* Repair Manual: A repair manual specific to your 1998 Chevy Astro is invaluable. It will provide detailed instructions, diagrams, and torque specifications.
This is a general guide. Always consult your vehicle's repair manual for specific instructions and torque values. Improper repair can lead to overheating and engine damage. Remember safety first!
