Depends on the vehicle and somtimes engine size. B Clear.
Best to get the shop manual but basically: Reomove Heater hoses from engine block and drain. Remove glove box. Disconnect cables that connect to heater core. Disconnect heater core from firewall. Disconnect hoses from heater core. Pull heater core from under dash.
Disconnect both heater hoses from heater core and connect them together
Disconnect heater core inlet and outlet hoses - couple them together
Disconnect them from heater core and with a coupling and 2 hose clamps tie them together
To change the heater core in a 1986 Toyota Supra, first disconnect the battery and drain the coolant. Remove the dashboard and climate control assembly to access the heater core housing. Disconnect the heater core hoses from the firewall, then unbolt and remove the heater core itself. Install the new heater core, reassemble the housing, dashboard, and reconnect the hoses, ensuring to refill the coolant before testing the system.
You have to pull the dash and all the lower fascia, then remove the box that houses the heater core. Take the clamps off the heater hoses from the engine compartment side of the firewall and disconnect the heater hoses. Disconnect the bracket that holds the heater core in place from the inside of the passenger compartment (if present.) Carefully remove the heater core and discard it. Install a new heater core reversing the above steps.
you should only have to take loose the heater hoses where they go into the firewall and of course the heater core itself
To replace the heater core on a 1989 Lincoln Mark VII, first, disconnect the battery and drain the coolant from the radiator. Remove the dashboard and the center console to access the heater box. Disconnect the heater hoses from the core, unbolt the heater box, and carefully remove the old heater core. Install the new heater core, reassemble the heater box, reconnect the hoses, and put the dashboard back in place before refilling the coolant and reconnecting the battery.
Loosen the clamps and carefully twist the hose where it connects to the heater core. If you are wanting to bypass the heater core, just run one of the hoses between the two places on the motor where they connect or put a short piece of pipe between the two hoses.
Could have a clogged line feeding the heater core. Disconnect return hoses from the heater core and verify coolant is flowing through the core.
Drain the radiator. disconnect the heater hoses as they go through the firewall. From inside of the cab, remove the heater core housing, then the core. Reverse the procedure to finish the installation.
You will see 2 heater hoses connected to the firewall. These are the inlet & outlet hoses going to the heater core. Disconnect them and then connect them together with a coupler. This will bypass the heater core.