The steam flows through a grill of pipes and the heat radiates from the pipes to the room.
no.....the heater would have to be leaking
Leak in heater core. Replace core.
You have a leaking heater core. you can try radiator sealer but that may only work for a short time.
heater core needs replacement
The heater core is leaking coolant.
Steam boilers work by boiling water to generate steam. The steam then is used to heat the engine.
The heater core is leaking coolant.
The steam could be coolant from a bad heater core.
replace the heater core, it most likely has a busted tube making the water heat and turn into steam whenever the heater or defroster is on. you may want to check the coolant level. after so long of the steam, or super heated water, escaping into the air duct system. you will obviously lose coolant level.
It could be steam from the heater core
Either your heater matrix (small radiator behind dash) or, more likely, a hose going into it has burst. Your heater won't work any more as all the hot water (the steam!) has came out of it. easy but awkward fix, do it yourself though, it's easy and will save you a small fortune.
Replace the heater core. It is leaking.