GMC 89018963 Core Asm,Auxiliary Heater

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To remove the front heater core, start by disconnecting the negative cable from the battery and draining the coolant. If you have a 1994 or earlier model, remove the coolant reservoir and windshield washer fluid reservoir mounting bolts. Loosen the clamps and detach the heater hoses from the core tubes, plugging the core tubes. Under the dash in the passenger compartment, remove the heater core cover screws and the core mounting screws at the rear of the core. Lift the core out of the housing. For installation, simply reverse the removal steps, refill the cooling system, and check for leaks. To remove the rear heater core, locate the optional auxiliary heater, which is floor mounted just ahead of the left rear wheel housing. Under the vehicle, disconnect the hoses from the heater core pipes. Inside the vehicle, remove the auxiliary heater cover and the band clamps on each side of the heater core, separating it from the heater module. Installation is the reverse of removal, and don't forget to refill the cooling system and check for leaks.