Q: How to remove and install a heater core in a Pontiac Grand Prix?
A: Disconnect the cable from the negative terminal of the battery. Caution: On models equipped with the Theftlock audio system, be sure the lockout feature is turned off before performing any procedure which requires disconnecting the battery. Raise the front of the vehicle and support it securely on jackstands. Apply the parking brake and block the rear wheels to keep the vehicle from rolling off the jackstands. Drain the cooling system. Remove the drain hose from the bottom of the heater case. Working in the passenger compartment, remove the panels from under the dash and the steering column trim covers. Also remove the floor console, if equipped. Remove the heater outlet duct and glove box. Remove the heater core cover. Disconnect the heater hoses from the heater core. On models where the heater pipes are not integral with the core, remove the metal clips where the heater core pipes enter the core, then twist and pull the two pipes out of the core. Remove the heater core. Caution: Have plenty of old towels on the floor to protect the carpet from spilled coolant. Installation is the reverse of removal. Refill the cooling system.