How to Replace the Heater Core in a Chevy Avalancheby Contributor; Updated November 07, 2017
Items you will need
J 43181 Quick Connect Connector Removal Tool
Clean, dry container for coolant
How to Replace the Heater Core in a Chevy Avalanche. Replacing the heater core on a Chevy Avalanche is challenging due to the sheer number of parts you must disconnect, and the fact that you'll need a special tool. Before attempting to replace the heater core in a Chevy Avalanche, make certain to have a J 43181 Quick Connect Connector Removal Tool or equivalent on hand in addition to a wrench set, screwdriver, and container for engine coolant.
Drain the engine coolant from your Cadillac Escalade into a clean container. Cover the container and set it aside for reuse. Then disconnect the negative battery cable and remove the air conditioning refrigerant. If you're not sure how to remove the refrigerant or don't have the proper equipment, do not attempt to improvise; have a more experienced friend help out.
Use the J 43181 quick connect tool to disconnect the inlet heater hose from the heater core; close the tool around the heater core pipe, firmly pull it into the quick connect end of the heater hose, then firmly grasp the heater hose and pull it forward to disconnect the inlet hose from the heater core. You will also need the J 43181 tool to disconnect the surge tank outlet hose from the heater core.
Remove or disconnect the accumulator, the instrument panel carrier, the HVAC module drain hose, all electrical harnesses and ground connections from the HVAC module, and the HVAC retaining nuts and bolts. Take the screws out of the heater core cover, remove the cover, remove the heater core cowl gasket from the heater core, and then pull the heater core itself out of the HVAC assembly.
Install the new heater core into the HVAC module. Inspect the heater core cowl gasket and replace it with a new one if necessary. Secure the HVAC module cover in place, then position the HVAC module and torque the mounting nuts to 90 inch pounds, the mounting bolts to 35 inch pounds.
Reconnect the HVAC module electrical connectors, then replace the instrument panel carrier, the accumulator, and attach the hoses to the heater core again. Make sure you hear an audible "click" when connecting the hoses; this is your guarantee that they are properly seated. Then reconnect the negative battery cable.
Refill the engine coolant system. Recharge the air conditioning refrigerant; if you don't have the proper equipment or knowledge to perform this step, get help from a mechanic or experienced friend.
Run the engine up to normal operating temperature. Check for proper climate control operation and verify that there are no coolant leaks.
Using the wrong tool in Step 2 may damage your heater core or the inlet heater hose. Always wait at least 2 minutes after disconnecting the negative battery cable before doing any sort of work on a vehicle with airbags. This wait period--and disconnecting the battery--is the only way to make certain the airbags will not accidentally deploy.