General Steps (Highly Simplified and Potentially Incomplete):
1. Preparation: Disconnect the negative battery terminal. Gather your tools: socket set, wrenches, screwdrivers (Phillips and flathead), pliers, coolant catch pan, new heater core, new O-rings (if needed), shop rags, and potentially a coolant flush kit. Consult a repair manual to identify all components involved.
2. Dash Removal (Most Difficult Part): This is the most labor-intensive step. You'll likely need to remove the steering column shroud, the radio, glove compartment, various trim panels, and possibly the instrument panel to access the heater core. This process involves removing numerous screws, clips, and connectors. Take pictures and/or make detailed notes as you go to aid in reassembly.
3. Heater Core Access: Once the dash is partially or fully disassembled, you'll need to access the heater core housing located behind the dash. This often requires removing parts of the HVAC system.
4. Heater Core Removal: Disconnect the heater core inlet and outlet hoses. Have your coolant catch pan ready to minimize coolant spillage. Carefully remove the old heater core from its housing. Note the orientation of the core and hoses for proper reinstallation.
5. Heater Core Installation: Install the new heater core, ensuring proper orientation. Connect the inlet and outlet hoses, using new O-rings if necessary.
6. Reassembly: Reinstall all the components removed in steps 2 and 3, carefully reversing the disassembly process. Ensure all connectors are securely fastened.
7. Coolant System Flush and Refill: Once reassembled, flush the entire cooling system to remove any debris or air pockets. Refill the system with the correct type and amount of coolant according to your vehicle's specifications. Bleed the air from the system as per your vehicle's instructions. Check for leaks.
8. Testing: Run the engine and heater to verify proper function and check for leaks.
Critical Considerations:
* Repair Manual: A factory repair manual or a reputable aftermarket manual specific to your 1999 Ford E-150 is absolutely essential. It will provide detailed diagrams, torque specifications, and specific procedures.
* Coolant: Use the correct type and concentration of coolant recommended for your vehicle.
* Safety: This job involves working with hot coolant and potentially sharp objects. Use caution and wear appropriate safety glasses and gloves.
* Complexity: This is a very complex repair, involving many small parts and delicate connections. One mistake can lead to significant further damage.
Again, unless you have extensive automotive experience and access to the proper tools and repair manuals, I strongly advise having a qualified mechanic perform this repair. The cost of a professional repair might be less than the cost of parts and your time if you make mistakes during the process.
