How do you change a heater core in a 1998 Chevy 1500? (video)
https://www.youtube.com/watch?v=zBOj0I6_wpw
Can clogged heater core cause overheating?
While your vehicle's heating system needs coolant to warm the interior, the engine needs coolant to keep it from overheating. If there is a clogged heater core, it will keep the coolant from flowing through the engine, causing it to overheat. via
How do bars stop leaking heater core? (video)
https://www.youtube.com/watch?v=6E2dEzxHejc