If your windshield tends to fog up when your BMW 2002 heater or defroster is on, you may have a pinhole leak in your heater core. Verify this by feeling into the heater and defroster outlets for moisture and for slime buildup. Since gaining access to a six-cylinder heater core is next to impossible, I resorted to Bar's Stop Leak. Added to the cooling system, this compound sealed the heater core leak instantly. Now I just hope that it doesn't plug up the rest of the system.
Author: Steve Brenneman
Now that the heater core leak is plugged, the rest of that compound is wandering around in your cooling system looking for a place to stick itself. Now is the time to backflush the cooling system to get rid of the excess sealer. You should have no problems after that.Tech Ed.