Passat 91 Coolant steam inside the car

Ok that's wired. I recentrly fixed my brakes problem on my Passat 91 now i have another issue. The car loose coolant for minutes. I haven't spot where the coolant is leaking yet but the most strange thing is that i can hear the coolant boiling and the steam comes out from the ventilation system inside the car. Any ideas?

Heater core....

Thanks for the fast reply i'll check it out and let you know if that fixed the problem.

BTW: a great place for VW service manuals is http://volkswagen.msk.ru/

Regards,
Vladimir

The heather core is the problem. It took me quite awhile to take the whole thing out since it's on a really inconvinient place but Success -=> i know what i need to buy on monday. I went on eBay,there are some for 45 USD w/shipping. When i check the prices tomorrow at the VW Dealer i'll buy the cheaper one :D. Thanks for the right directions.

laterz