Corrosion.
Broken or split hose Radiator leak heater core leak
Heater core is shot, its monted on the firewall behind center console/instrument cluster. When turning on heater fan, will dischrge coolant out of the vent. Replace heater core to resolve the leak
Heater core could be clogged.
At the heater core itself.
if you smell it inside, it's the heater core it has a leak.
Leak in heater core. Replace core.
You may have a clogged heater core, or a leak in the system somewhere. Take your car to a mechanic who can replace the heater core or diagnose the leak.
Your heater core is leaking you probably also noticed the heater may not be working as well.
plugged evaporator drain tube or the heater core has gone bad
caused by leaking heater core not radiator heater it is under the dash hard ot get to if the leak is not to big use radiator stop leak otherwise fix is going to be big bucks
The heater core or a hose to the heater core has a leak. Hopefully it's a hose under the hood because it's a very involved process to get the heater core out.
heater core has a leak replace heater core