Before you start:
* Safety First: Disconnect the negative battery cable. Allow the engine to cool completely. Wear safety glasses and gloves.
* Gather Tools and Parts: You'll need a repair manual, new water pump, new gasket, coolant, new thermostat (highly recommended), socket set (metric), wrenches, screwdrivers, pliers, drain pan, jack stands (essential!), and possibly a radiator flush kit.
* Consult a Repair Manual: A Haynes or Chilton manual for your specific year and engine is crucial. Pictures and diagrams are invaluable.
General Steps (These are generalized and may not apply perfectly to your specific Blazer):
1. Drain the Coolant: Locate the radiator drain petcock (usually at the bottom of the radiator) and carefully drain the coolant into a large drain pan. You might also need to drain the engine block; check your manual.
2. Remove Drive Belts: Remove the serpentine belt or the individual belts (depending on your engine) to access the water pump. This usually involves loosening tensioners. Diagram your belt routing before removal!
3. Remove Accessory Components: You might need to remove or loosen various components like pulleys, hoses, or brackets to gain access to the water pump. This varies widely depending on your engine.
4. Remove the Water Pump: This usually involves removing several bolts holding the water pump to the engine block. Be prepared for stubborn bolts – penetrating oil can help. Once the bolts are out, carefully remove the old water pump.
5. Clean the Mounting Surface: Thoroughly clean the engine block's mating surface where the water pump sits to ensure a good seal.
6. Install the New Water Pump: Apply a thin, even layer of gasket sealant (if recommended by the manufacturer) to the new gasket. Carefully install the new water pump, aligning it correctly, and secure it with the bolts. Torque the bolts to the specifications in your repair manual.
7. Replace the Thermostat (Highly Recommended): While you have things apart, it's a good idea to replace the thermostat. It's relatively inexpensive and a failure could ruin your new water pump.
8. Reinstall Components: Reinstall any components you removed in step 3. Reinstall the drive belts, ensuring correct routing.
9. Reattach Hoses: Carefully reconnect all coolant hoses to the water pump and radiator.
10. Refill Coolant: Slowly refill the radiator and coolant reservoir with the correct type of coolant for your engine (check your manual). Consult your manual on the correct coolant mixture (usually 50/50 coolant and distilled water).
11. Bleed the Air: Start the engine and let it run until the thermostat opens. Check for leaks. Add more coolant if needed. You may need to bleed the cooling system to remove any trapped air. Your repair manual will show you how.
12. Test for Leaks: Let the engine run for a while and carefully inspect for any leaks around the water pump and hoses.
Important Considerations:
* Engine Type: This process varies significantly depending on whether you have a 4.3L V6, 5.7L V8, or other engine. Your repair manual is essential.
* Torque Specifications: Using the correct torque specifications is critical to prevent damage.
* Coolant Type: Use the correct type of coolant recommended for your Blazer.
* Professional Help: If you are not comfortable performing this repair, consider seeking professional help from a mechanic. Improper repair can lead to serious engine damage.
This is a general overview. Always consult a repair manual specific to your 1999 Chevy Blazer's engine before attempting this repair. Improper installation can result in serious engine damage.
