Will a leaking heater core cause your car to overheat?
A leaking heater core will cause the engine to overheat because the coolant is leaking out.
Not necessarily. It depends on what you mean by a bad heater core. The core will either be leaking or stopped up. If it is leaking, then it can cause the engine to overheat and the only fix is to replace it. A clogged or plugged heater core can sometimes be fixed by flushing it. You can also temporarily bypass the heater core until you can get it fixed. Just connect the inlet & outlet…
If your heater core is LEAKING engine coolant so that your engine coolant level drops too low or the engine coolant is lost completely and causes your engine to overheat then your engine can be damaged beside the mess the leaking coolant makes inside your vehicle ( you might be able to just temporarily bypass the heater core so that no engine coolant is flowing through the heater core )