Not practical to try to fix a heater core. Replace it with a new one.
Try the repair tips on the Autozone web site.
To replace the heater core in a 1965 Buick Riviera, start by disconnecting the battery and draining the coolant. Remove the dashboard and any components obstructing access to the heater box. Unbolt the heater core from the heater box, replace it with a new unit, and reassemble everything in reverse order. Finally, refill the coolant, reconnect the battery, and check for leaks.
To change the heater core on a 1989 Buick Riviera, first disconnect the battery and drain the coolant. Remove the dashboard and HVAC housing to access the heater core, which is typically located behind the firewall. Detach the hoses connected to the heater core, and then remove the mounting screws to take out the old core. Install the new heater core by reversing the process, ensuring all connections are secure before reassembling the dashboard and refilling the coolant.
Does it have a funny smell? it could be leaky heater core
I believe that is a bypass tee that allow coolant to go to your heater core for your heater.
How do I replace heater core on 98 Buick lesabre
replace heater core on 92 buick century
How do you install a heater core on a 1998 buick lesabre
Under dash, passenger side, inside the vehicle, mounted on the firewall.
The heater core is mounted to the passenger side firewall on the 1988 Buick Electra 307. The blower motor needs to be removed to access the heater core.
It's in the heater core housing.
It could be the heater core leaking.