Here's a general procedure. Specifics might vary slightly depending on your exact engine (4.3L V6 is most common, but there might be others):
1. Disconnect the Battery: This is crucial to prevent accidental shorts. Disconnect the negative (-) terminal first.
2. Cool Down: Allow the engine to cool completely. A hot engine means a hot water pump and fan clutch, increasing the risk of burns.
3. Gather Tools: You'll need:
* Socket wrench: The size will depend on the fan clutch nut; it's usually a large nut (likely 1 1/16" or 1 5/16", but double-check your vehicle's specifications).
* Wrench: A large open-ended or box-end wrench may be needed to hold the water pump pulley in place while you loosen the nut. A wrench the same size as the socket will be necessary to counter-hold the pulley. If there's limited space, a pipe wrench might help on the pulley; it's possible to put it on the pulley itself or the outer edge of the pulley.
* Penetrating Oil (PB Blaster or similar): Spray this generously on the fan clutch nut several hours before attempting removal to help loosen any rust or corrosion. Let it soak.
* Gloves: Protect your hands.
* Jack Stands (Highly Recommended): Support the front of the vehicle securely on jack stands. Never work under a vehicle supported only by a jack.
* Ratchet and extensions: To reach the nut easily.
4. Access: You'll need to access the fan clutch from the front of the engine. This may involve removing some parts depending on your access. Consult a repair manual specific to your year and engine to see if other components need to be moved.
5. Loosen the Nut: Use the socket wrench and ratchet to loosen the fan clutch nut. It will be very tight, so be prepared for resistance. Simultaneously, hold the water pump pulley stationary with your wrench to prevent it from turning. If the nut is very stuck, try using a breaker bar for added leverage.
6. Remove the Clutch: Once the nut is loose, unscrew it completely. The fan clutch should then pull off.
Important Considerations:
* Repair Manual: A repair manual specific to your 1996 Chevy Astro van is highly recommended. It will provide diagrams, torque specifications, and step-by-step instructions tailored to your vehicle.
* Fan Clutch Removal Tool: There are specialized tools available to remove stubborn fan clutches, especially if you have trouble holding the pulley still. They prevent damage to the water pump.
* Water Pump: Inspect the water pump while you have access to it. If it shows signs of wear or leakage, consider replacing it at the same time to avoid future problems.
If you're not comfortable performing this repair yourself, it's best to take your Astro to a qualified mechanic. Improper removal can damage the water pump or other components.
