Here are the instructions for your heater core.
Disconnect the negative battery cable.
After disconnecting the negative battery cable, wait at least 60 seconds before working on the SRS module or instrument panel.
Drain the cooling system into a clean container for reuse.
Disconnect the heater hoses from the heater core at the firewall.
To prevent damage to the air bag control unit during removal or installation of the floor console, avoid shocks or impact. Do not drop.
Remove the floor console by removing or disconnecting the following:
Shift lever knob on manual transmission vehicles or the shift indicator plate on automatic transmissions
Coin holder behind the shifter, then the center console trim cover in front of the shifter
Center console retaining bolt cover plugs, then remove the bolts
Console assembly, then the brackets
Remove or disconnect the following:
Steering column covers
Instrument cluster bezel and then the instrument cluster
Instrument panel switch, hood lock release handle and the lower duct work
Driver's knee protector and the left side air outlet cover
Center panel assembly
Glove box undercover, then the glove box and the right side panel cover
Radio and cup holder
Cables from the heater assembly and the blower, then pull out the heater control panel assembly, noting the location of the boss in the center reinforcement
Cool air bypass damper lever cable connection
Passenger's side air bag module and disconnect the harness connector, if equipped
Steering column bolts and lower the column
Harness connector at the lower left side of the instrument panel
Instrument panel mounting hardware and remove the instrument panel from the vehicle
Joint duct between the heater case and the blower assembly (on models without air conditioning)
Both stamped steel center reinforcement piece
Evaporator retaining nut and remove the heater case assembly, if equipped with air conditioning
Heater core from the case
Exploded view of the heater core, heater housing and related components-1999-2003 Galant
Install or connect the following:
Heater core to the case
Evaporator retaining nut and Install the heater case assembly, if equipped with air conditioning
Both stamped steel center reinforcement pieces
Instrument panel and install the instrument panel mounting hardware
Steering column bolts
Passenger's side air bag module and connect the harness connector, if equipped
Cables to the heater assembly and the blower and install the heater control panel assembly
Left side air outlet cover and the driver's knee protector
Lower duct work, the instrument panel switch and hood lock release handle
Instrument cluster and the instrument cluster bezel
Install the floor console installing or connecting the following:
Console assembly brackets and the console
Center console retaining bolts, then the bolt cover plugs
Heater hoses to the heater core at the firewall
Refill the cooling system.
Connect the negative battery cable.
Operate the engine to normal operating temperatures; then, check the climate control operation and check for leaks.