Here's a general outline of the process. Always consult a repair manual specific to your year, make, and model before attempting this repair. Differences in engine, cab style (regular, extended, crew), and options can drastically alter the procedure.
1. Preparation:
* Safety First: Disconnect the negative battery cable. Wear safety glasses and gloves.
* Gather Tools and Parts: You'll need a complete set of metric sockets and wrenches, screwdrivers (Phillips and flathead), pliers, a coolant recovery tank (or large container to catch coolant), a new heater core, new O-rings (if needed), and potentially new hoses. A shop manual is crucial for torque specifications. Consider renting a hose clamp tool if you don't own one.
* Drain the Coolant: Completely drain the engine coolant system. Locate the drain petcock(s) on the engine block and radiator.
* Prepare the Workspace: This job often requires ample space and good lighting. Consider working in a well-ventilated area.
2. Accessing the Heater Core:
This is the most challenging part and varies significantly based on your truck's model. Generally, it involves:
* Dash Removal (Partial or Complete): Expect to remove parts of the dashboard, steering column shroud, and potentially the glove box. This process involves numerous screws, clips, and potentially disconnecting electrical connectors. Your repair manual will detail the exact steps.
* Evaporator Core Removal (Often Necessary): In many cases, you'll need to remove the evaporator core (A/C component) to access the heater core.
* Accessing the Heater Core Housing: Once the dashboard components are removed, you'll find the heater core housing, which is usually located behind the dashboard.
3. Heater Core Replacement:
* Disconnect the Heater Core Hoses: Carefully disconnect the hoses connected to the heater core. Have rags ready to absorb any remaining coolant.
* Remove the Heater Core Housing: This often involves removing several screws or bolts.
* Remove the Old Heater Core: Carefully remove the old heater core from the housing. Note the orientation of the core and any clips or retainers.
* Install the New Heater Core: Carefully install the new heater core, ensuring it's properly seated and oriented.
* Reassemble the Heater Core Housing: Reinstall the housing, ensuring all components are properly secured.
4. Reassembly:
* Reconnect the Heater Core Hoses: Reconnect the heater hoses, using new clamps if necessary.
* Reinstall Dashboard Components: Carefully reinstall all removed dashboard components, paying close attention to electrical connectors and clips.
* Refill the Coolant System: Refill the coolant system with the correct type and amount of antifreeze/coolant mixture. Refer to your owner's manual.
* Bleed the Air from the System: Bleed any trapped air from the cooling system. This typically involves opening bleed valves and running the engine until coolant flows freely from them.
* Test the System: Start the engine and run it for a while, checking for leaks and ensuring the heater is functioning correctly.
Disclaimer: This is a highly simplified overview. The actual process is far more complex and requires precise steps and attention to detail. Incorrect installation can lead to leaks, overheating, and further damage. Use a repair manual specific to your 1996 Chevy truck model to obtain the proper instructions and diagrams. If you are not comfortable performing this repair, it is strongly recommended to take your truck to a qualified mechanic.
