How do you change a heater core on a 1998 Ford Econoline V8 air 250?
Drain the engine cooling system. Disconnect the battery ground cable. Disconnect the quick disconnect heater hose couplings at the heater core. This requires a special tool that is available from some auto parts stores. Remove the engine cover. Remove the instrument panel finish panel at the passenger's end of the dash where you would find a glove box if there were one. Remove the heater core cover which is held on with seven screws. Remove the heater core.
To install, reverse the removal procedure.