Q: How do you remove the heater core on Mercury Grand Marquis?
A: Taking out the heater core is a process that involves disconnecting the negative battery cable and draining the cooling system. One needs to unplug the tubes on the heater hoses from the core. One must also remove nuts as well as vacuum hoses. Other interior trim parts, like instrument panel trim, steering column covers, and reinforcement brace, need to be removed. The door sill plates should be loosened, cowl trim panels removed, and instrument panel bolts taken out. After lowering the steering column, retaining screws are removed to pull back the instrument panel. Wiring harnesses and vacuum components are disconnected from it. The floor air distribution duct is then removed. Move the plenum and remove it too.