Here's a *general* overview of the steps involved. This is not a complete guide and may not be accurate for your specific vehicle. Always refer to a repair manual.
1. Preparation:
* Safety First: Disconnect the negative battery terminal.
* Gather Tools: You'll need a variety of tools including sockets, wrenches (metric), screwdrivers (Phillips and flathead), pliers, a coolant drain pan, a new heater core, new O-rings, coolant, and possibly a special tool to compress the heater core hoses. A shop manual will list the specific tools.
* Drain Coolant: Drain the engine coolant completely. This is crucial to minimize mess and coolant loss.
* Access the Heater Core: This is the most difficult part. In a 1990 Grand Caravan, access usually requires removing significant parts of the dashboard, potentially including the instrument panel and possibly even the steering column. The repair manual will provide detailed instructions on this.
2. Removal of the Old Heater Core:
* Disconnect Hoses: Carefully disconnect the heater core hoses. Be prepared for some coolant spillage even after draining.
* Remove the Heater Core Housing: This often involves removing screws, clips, and potentially other components that are obstructing access. The repair manual will guide you through this step.
* Remove the Heater Core: Once the housing is accessible, remove the old heater core carefully. It is often fragile and can be easily damaged.
3. Installation of the New Heater Core:
* Install New O-rings: Install new O-rings on the new heater core.
* Install the New Heater Core: Carefully install the new heater core into the housing, ensuring it sits correctly.
* Reassemble the Housing: Reassemble the heater core housing, paying attention to the correct orientation of all parts.
4. Reassembly:
* Reconnect Hoses: Reconnect the heater hoses, ensuring a tight seal.
* Reinstall Dashboard Components: Carefully reinstall all the dashboard components you removed, working in reverse order of removal. This is a meticulous process requiring attention to detail.
* Refill Coolant: Refill the cooling system with the correct type and amount of coolant. Bleed the air from the system to prevent overheating. Consult your repair manual for the correct bleeding procedure.
5. Testing:
* Test the Heater: Start the engine and test the heater to ensure it is working correctly. Check for leaks.
Important Considerations:
* Repair Manual: Obtain a factory service manual or a reputable repair manual specific to your 1990 Dodge Grand Caravan. This is absolutely essential for successful completion of this task.
* Complexity: This is a very involved repair. If you are not comfortable with this level of automotive repair, it's strongly recommended to take your vehicle to a qualified mechanic. The cost of making a mistake can be far greater than the cost of professional repair.
* Hidden Damage: While replacing the heater core, you might discover other issues with the HVAC system. Be prepared for unexpected repairs.
This overview is highly generalized. The actual process will be much more intricate. Do not attempt this repair without consulting a detailed repair manual specific to your vehicle. Incorrectly performing this repair can lead to significant damage to your vehicle. If you're unsure, seek professional help.
