Disclaimer: This information is for guidance only. Working on your vehicle carries inherent risks. If you're uncomfortable performing this repair, take it to a qualified mechanic.
Tools You'll Likely Need:
* Repair manual specific to your 1999 GMC Jimmy and engine
* Socket wrench set (metric)
* Wrenches (metric)
* Ratchet and extensions
* Pliers
* Screwdrivers (Phillips and flathead)
* Drain pan
* New water pump (ensure it's the correct one for your engine)
* New gasket(s) and seals for the water pump
* Antifreeze/coolant
* Jack and jack stands (essential for safety)
* Wheel chocks
* Torque wrench
* New thermostat (recommended while you're in there)
Steps (General):
1. Safety First: Disconnect the negative battery terminal. Place the vehicle on jack stands after securely jacking it up. Always work in a well-ventilated area.
2. Drain the Cooling System: Locate the drain plug on the engine block (usually low on the radiator). Place your drain pan underneath and carefully open the drain plug to allow the coolant to drain completely. This may take some time.
3. Remove the Fan and Fan Shroud (if applicable): Depending on your engine, you might need to remove the fan and/or the fan shroud to access the water pump. This usually involves removing bolts or clips.
4. Remove the Serpentine Belt: Use a belt tensioner tool to release the tension on the serpentine belt and remove it. Diagram the belt routing before removing it to ensure correct reinstallation.
5. Disconnect the Water Pump: Disconnect the upper and lower radiator hoses from the water pump. They may be clamped, so you'll need pliers to loosen or remove the clamps.
6. Remove the Water Pump Pulley (if applicable): Some water pumps have a pulley that needs to be removed before the pump itself. This may involve removing bolts.
7. Remove the Water Pump Bolts: Carefully remove the bolts securing the water pump to the engine block. These are often difficult to access, so patience and the right tools are crucial.
8. Remove the Old Water Pump: Once all the bolts are removed, carefully remove the old water pump. Take note of the orientation of the pump and the gasket.
9. Clean the Mounting Surface: Thoroughly clean the engine block surface where the water pump mounts to remove any old gasket material. This ensures a good seal with the new pump.
10. Install the New Water Pump: Apply a thin, even layer of gasket sealant (if specified by the manufacturer) to the new water pump gasket. Carefully install the new water pump, ensuring it's properly seated.
11. Install the Water Pump Bolts: Install the water pump bolts and tighten them to the manufacturer's specified torque. Use a torque wrench to avoid over-tightening.
12. Reinstall the Pulley (if applicable): Reinstall the water pump pulley (if applicable).
13. Reconnect the Hoses and Belt: Reconnect the upper and lower radiator hoses to the water pump. Reinstall the serpentine belt, following the routing diagram you made earlier.
14. Reinstall the Fan and Shroud (if applicable): Reinstall the fan and shroud.
15. Refill the Cooling System: Carefully refill the cooling system with the correct type and amount of antifreeze/coolant. Refer to your owner's manual for the correct mixture ratio.
16. Bleed the Air from the Cooling System: Run the engine until it reaches operating temperature. Check for leaks and carefully bleed any air pockets from the system according to your repair manual.
17. Check for Leaks: After the engine cools, carefully inspect all connections for leaks.
18. Reconnect the Battery: Reconnect the negative battery terminal.
This is a simplified overview. The exact procedure may differ based on your specific GMC Jimmy model and engine. Refer to your repair manual for detailed instructions, torque specifications, and safety precautions. Again, if you are not comfortable performing this repair yourself, please seek professional assistance from a qualified mechanic.
