The best way to find out is go to your local auto parts store, ask for a haynes or chiltons manual on your vehicle. This will tell you everything you need to know about working on your vehicle. Its alot of work that takes alot of patience.
Could be a bad thermostat or heater core
possible leak in heater core.
Could be a bad thermostat or heater core
it's on the outside on the passenger side.near the heater core hoses.
Under dash, passenger side, inside the vehicle, mounted on the firewall.
Low coolant? Heater core airbound, restricted, or plugged? Bad thermostat? Water pump not circulating coolant?
Probably a worn-out or clogged heater core.
Its either a bad heater core or a clogged one. They are very expensive.
replace heater core on 92 buick century
How do I replace heater core on 98 Buick lesabre
How do you install a heater core on a 1998 buick lesabre
Try the repair tips on the Autozone web site.