How to replace the heater core on 02 optima

Ted Harris, try this:

Before servicing the vehicle, refer to the Precautions Section.

Disconnect the negative battery cable.

CAUTION

After disconnecting the negative battery cable, wait for at least 10 minutes for the SRS module to deplete its stored energy.

Recover the refrigerant.

Drain the cooling system.

Remove the expansion valve from the evaporator core and plug the lines.

Disconnect the heater hoses from the heater unit.

Remove the crash pad as follows:

• Remove the front seat.
• Tilt the steering column down and remove the center facia panel.
• Disconnect the trip sensor connector and remove the gauge cluster.
• Remove the heater control unit.
• Remove the radio unit.
• Disconnect the damper from the glove box.
• Remove the glove box from the lift, disconnect the pin and remove the glove box.
• Remove the crash pad side cover.
• Remove the center under cover.
• Remove the console side cover.
• Crash pad lower panel mounting.
• Remove the A-pillar trim
• Remove the photo sensor.
• Disconnect the passenger air bag connector.
• Remove the crash pad.

Remove the cowl cross bar assembly.

Remove the heater unit.

Disconnect the heater from the blower unit.

Remove the heater core cover and remove the heater core.

Click image to see an enlarged view

Fig. Crash pad exploded view-Optima

Fig. Heater core from the heater unit-Optima

Installation is the reverse of removal.

Refill the cooling system to the correct level.

Start the engine and check for leaks.

information is from here. Hope this helps, good luck.