Help: Smoking Dashboard, Coolant leaking!

I have a Bmw 1985 and while i was driving i turned the temperature to 71
which is in the middle, volume was on 0. My heater doesnt work well and
activates late after a few seconds. Then suddenly smoke was coming from the
dashboard and when i pulled over i saw coolant leaking on the bottom of the
car  and a tiny amount below my seat (right on the brakes).

what do you think is the cause? is this a major problem? or just piping for
the heater which blew up and only means i wont have heat this winter?

please help.