Tools You'll Need:
* Repair Manual: Essential for specific torque specs and diagrams.
* Socket Set (metric): Various sizes, including deep sockets.
* Wrench Set (metric): Open-ended and combination wrenches.
* Ratchet: With extensions and possibly a universal joint.
* Pry Bar: For stubborn components.
* Screwdrivers: Phillips and flathead.
* Drain Pan: To catch coolant.
* New Water Pump: Make sure it's the correct one for your Astro's engine.
* New Thermostat (recommended): Replace it while you're in there.
* New Gasket(s): For the water pump and thermostat housing.
* Coolant: The correct type and amount for your Astro.
* Jack and Jack Stands: For safe vehicle support.
* Gloves: To protect your hands.
* Safety Glasses: To protect your eyes.
Steps:
1. Prepare the Vehicle: Park on a level surface, engage the parking brake, and chock the wheels. Jack up the front end and secure it on jack stands.
2. Drain the Coolant: Locate the radiator drain petcock (usually at the bottom of the radiator) and carefully open it, letting the coolant drain into your drain pan.
3. Remove the Serpentine Belt: This typically involves loosening the tensioner pulley. Consult your repair manual for the specific procedure; it often involves using a special tool or a wrench on a specific bolt.
4. Remove the Fan and Fan Shroud (if applicable): This may involve removing bolts or clips holding the shroud to the radiator. Sometimes the fan is attached to the water pump, requiring removal of additional parts.
5. Remove the Water Pump Pulley (if applicable): This may require a special pulley puller.
6. Remove the Water Pump: This is the most challenging part. You'll likely need to remove several bolts holding the water pump to the engine block. These bolts can be stubborn; use penetrating oil and patience. Be careful not to damage the gasket surface on the engine block.
7. Clean the Mounting Surface: Thoroughly clean the engine block's mating surface where the water pump sits, removing any old gasket material.
8. Install the New Water Pump: Apply a thin, even bead of gasket sealant (if recommended by the manufacturer) to the new water pump gasket. Carefully align the new pump and install the bolts, tightening them in a star pattern to ensure even pressure. Use the correct torque specification from your repair manual.
9. Install the Thermostat (if replacing): Install the new thermostat and gasket according to your repair manual.
10. Reinstall the Water Pump Pulley (if applicable): If you removed it.
11. Reinstall the Fan and Fan Shroud (if applicable):
12. Reinstall the Serpentine Belt: Route the belt correctly according to the diagram in your repair manual.
13. Refill the Cooling System: Carefully refill the radiator and overflow reservoir with the correct type of coolant. Refer to your owner's manual for the proper coolant mixture (usually a 50/50 mix of coolant and distilled water).
14. Bleed the Air from the Cooling System: This is crucial to prevent overheating. Run the engine until it reaches operating temperature, checking the coolant level and adding more as needed. Some vehicles have specific bleeding procedures; check your repair manual.
15. Check for Leaks: Inspect the water pump and surrounding area for any leaks.
16. Lower the Vehicle: Carefully lower the vehicle from the jack stands.
17. Final Check: After driving for a while, check the coolant level again and look for any signs of leaks.
Important Considerations:
* Repair Manual: This is not a substitute for a detailed repair manual specific to your 1997 Chevy Astro. The steps and specifics may vary slightly depending on the engine.
* Professional Help: If you're uncomfortable performing this repair yourself, consider taking it to a qualified mechanic.
This guide provides a general overview. Always consult a repair manual and exercise caution when working on your vehicle. Improper repairs can lead to engine damage.
