1. Preparation:
* Safety First: Disconnect the negative battery terminal. This prevents accidental short circuits.
* Gather Tools: You'll need various tools, including screwdrivers (Phillips and flathead), wrenches (metric), pliers, a socket set, possibly a drain pan, coolant recovery system, and potentially specialized tools for removing the dash. A repair manual will list the specific tools.
* Consult a Repair Manual: This is crucial! A Chilton's or Haynes manual will provide detailed diagrams and instructions specific to your vehicle. This is far superior to general instructions.
* Drain the Coolant: Completely drain the engine's cooling system. This is essential to prevent a coolant mess.
2. Accessing the Heater Core:
* Dashboard Removal (Most Difficult Part): This is the most time-consuming and challenging part. You'll likely need to remove parts of the dashboard, possibly the glove box, radio, and other components to gain access to the heater core. This often involves removing screws, clips, and potentially disconnecting electrical connectors. The repair manual is vital here. Take pictures as you go to aid reassembly.
* Evaporator Core (If Applicable): If you have A/C, the evaporator core is usually located near the heater core. You may need to disconnect the AC system and potentially evacuate the refrigerant using proper equipment and procedures before working on the heater core. Improper handling of refrigerant is dangerous and illegal.
3. Removing the Heater Core:
* Disconnect Heater Core Hoses: Carefully disconnect the heater core inlet and outlet hoses. Have rags ready to absorb any remaining coolant.
* Remove the Heater Core: Once access is gained, the heater core itself is typically held in place by brackets or clips. Carefully remove these fasteners and slide the heater core out. This can be tricky due to limited space.
4. Installation:
* Install the New Heater Core: Carefully install the new heater core, ensuring it's properly seated.
* Reconnect Hoses: Reconnect the heater hoses.
* Reassemble Dashboard: Reinstall the dashboard components in reverse order of removal. Again, your photos are critical.
* Refill and Bleed Cooling System: Refill the cooling system with the correct type of coolant and bleed it to remove air pockets. This is important for proper engine cooling.
* Check for Leaks: After reassembly, carefully check for any coolant leaks.
Important Considerations:
* A/C System: If you have A/C, you may need to have it professionally evacuated and recharged. Improper handling of refrigerant can be harmful.
* Complexity: This is a very involved job, and it's easy to damage parts of the dashboard or make mistakes during reassembly.
* Professional Help: If you're not comfortable performing this repair yourself, it's best to take your van to a qualified mechanic. The cost of professional repair might be less than the cost of parts and the potential for additional damage if you attempt it yourself.
This is a general outline, and specifics will differ greatly depending on your vehicle. Refer to a repair manual specific to your 1989 Chevy G20 van. Attempting this repair without the proper knowledge and tools can lead to damage and frustration. Safety is paramount – always disconnect the battery before working on the electrical system.
