Safety First!
* Disconnect the negative battery terminal before starting any work to prevent accidental shorts.
* Allow the engine to cool completely before working on it to avoid burns.
* Wear safety glasses to protect your eyes from debris.
* Use jack stands if you're working under the vehicle. Never rely solely on a jack.
* Dispose of used coolant properly.
Tools and Materials:
* Repair manual specific to your 1991 Ford F-150 4.9L
* Socket set (metric)
* Wrenches (metric)
* Screwdrivers (Phillips and flathead)
* Pliers
* Drain pan
* New water pump (ensure it's the correct one for your engine)
* New gasket(s) (for the water pump and possibly the thermostat housing)
* New coolant (50/50 mix of coolant and distilled water)
* Hose clamps
* Radiator flush
* Rags or shop towels
* Torque wrench
Procedure:
1. Drain the coolant: Locate the radiator drain petcock (usually at the bottom of the radiator) and carefully open it to drain the coolant into your drain pan. You might also need to drain the engine block; consult your repair manual for the location of the drain plug.
2. Remove the serpentine belt: Use a belt tensioner tool (or the appropriate method for your truck – some have manual tensioners) to release tension on the belt and remove it. Diagram the belt routing before removing it to aid reinstallation.
3. Remove the fan and shroud (if applicable): This might involve removing the fan clutch and/or shroud bolts. Be careful, the fan and shroud can be heavy.
4. Remove the water pump pulley (if applicable): Some models have a separate pulley; others might have the pulley integrated into the water pump. Use the appropriate socket and wrench to remove the pulley bolts.
5. Remove the water pump bolts: These are usually located around the perimeter of the water pump. Carefully remove these bolts, keeping track of their location and order. They may be different lengths.
6. Remove the old water pump: Gently pry the old water pump away from the engine block. It might be slightly stubborn due to corrosion; use a pry bar carefully to avoid damaging the engine block.
7. Clean the mating surfaces: Thoroughly clean the engine block mating surface and the new water pump mating surface with a wire brush, ensuring they're free of debris and old gasket material.
8. Install the new water pump: Apply a thin, even bead of gasket sealant (if recommended by the manufacturer – check your new pump's instructions) to the new gasket. Carefully install the new water pump, ensuring it's seated correctly. Install the bolts, tightening them in a star pattern to ensure even pressure. Use a torque wrench and consult your repair manual for the correct torque specifications.
9. Reinstall the water pump pulley (if applicable): Reinstall the pulley, tightening the bolts to the specified torque.
10. Reinstall the fan and shroud (if applicable):
11. Reinstall the serpentine belt: Refer to your diagram or repair manual to ensure correct routing.
12. Refill the cooling system: Add the 50/50 coolant mixture to the radiator until it's full. You might need to use a funnel. Consult your repair manual to find the correct capacity.
13. Bleed the cooling system: Run the engine, allowing it to reach operating temperature. Check for leaks around the water pump and other connections. Bleed the air out of the system as needed (refer to your repair manual for specific bleeding instructions).
14. Check coolant level: After the engine has cooled, check the coolant level and top it off if necessary.
Important Notes:
* This is a simplified guide. Always consult your repair manual for specific instructions and torque specifications for your vehicle.
* If you are not comfortable performing this repair, it's best to take your vehicle to a qualified mechanic. Incorrect installation can lead to engine damage.
* Consider replacing the thermostat while you're at it, as it's relatively easy to access once the water pump is removed.
Remember to always prioritize safety and consult your repair manual for specific instructions relevant to your vehicle. Good luck!
