Here's a high-level summary of the process:
1. Preparation: This is crucial. You'll need a clean, well-lit workspace, a complete set of tools (including various sockets, wrenches, screwdrivers, a torque wrench, and possibly a harmonic balancer puller), jack stands, engine hoist (highly recommended), new oil pump gasket(s), new oil pan gasket, new oil filter, new oil, and a drain pan. Consult a repair manual to identify all necessary parts.
2. Drain the Oil: Drain the engine oil completely.
3. Remove the Oil Pan: This often requires removing various components that are in the way, potentially including exhaust manifolds, parts of the steering linkage, and possibly even the front driveshaft. Access is tight. The oil pan itself will likely be bolted to the engine block.
4. Remove the Oil Pump: Once the oil pan is removed, you'll see the oil pump. It's usually bolted to the engine block. This will involve removing various bolts and potentially dealing with a timing chain cover (which may or may not need to be partially or fully removed, depending on the specific engine design). Be very careful not to damage the oil pump pickup tube while removing the oil pump.
5. Install the New Oil Pump: Install the new oil pump, ensuring the gasket is properly seated and lubricated. Torque the bolts to the specifications given in your repair manual. Pay close attention to the oil pump alignment and its relationship with the timing chain or gears. This is a critical step.
6. Reinstall the Oil Pan: Carefully reinstall the oil pan with a new gasket, ensuring it's properly seated and all bolts are tightened to the correct torque specifications.
7. Reassemble Everything: Reinstall all the components removed in steps 3 and 4. This is a reverse order of disassembly but requires careful attention to detail.
8. Refill with Oil and Check for Leaks: Once everything is reassembled, refill the engine with the correct amount and type of oil. Carefully check for any oil leaks around the oil pan and pump. Run the engine for a short period, then check the oil level again.
Critical Considerations:
* Timing Chain/Gears: Accessing the oil pump might involve working around the timing chain or gears. If you're not familiar with how to properly time the engine, this is a job best left to a professional. Improper timing can cause serious engine damage.
* Engine Hoist: An engine hoist can significantly simplify this process, allowing you to safely lower the engine slightly to improve access.
* Repair Manual: A factory service manual is absolutely essential. It will provide detailed diagrams, torque specifications, and the correct procedure for your specific engine.
This is a complex job. If you are not comfortable with engine repair, it's strongly recommended that you take your Grand Wagoneer to a qualified mechanic. The cost of a professional repair will likely be less than the cost of damaging your engine due to an improper repair.
