If removing the front heater core, discharge the air conditioning system first, but this isn't needed for rear heater core removal. Disconnect the battery's negative cable and drain the cooling system. For models except 2007 Acura MDX: Mark the heater control valve cable before disconnecting. Detach the heater hoses and evaporator lines at the firewall. Remove the heater core, evaporator housing, and instrument panel. Installation follows the removal steps in reverse. For the 2007 Acura MDX: Disconnect the air conditioning lines and remove the heater core housing. Access the lower heater duct by folding the carpet back. Slide the housing towards the vehicle's rear to remove. For the rear heater core: Remove the center console, detach heater hoses, and adjust the housing to extract the heater core. Installation mirrors removal. After all procedures, reconnect the battery, refill the cooling system, and have the AC system serviced.