Jaime, I have preached to this list about Bar's Leak for a while now so some
folks are probably sick of hearing this.  I would not use it as it coats the
inside of your radiator, heater core, and who knows what else and can cause
the heat transfer of these items to become inefficient and eventually cause
you to have to replace the radiator or heater core (neither of these is a
cheap item).
I recommend Moroso Ceramic Block sealer.  You can buy it at any local speed
shop for about $15.  It works excellent and just seals the leak but doesn't do
anything to gum up the rest of the cooling system.  I don't sell this stuff
but it is a great product and I would almost recommend anyone taking a cross
country trip in a Vanagon to have a bottle on hand in case of emergency.
Hope this helps.
Ken Wilford
Van-Again
John 3:16
PS I know the I will now get emails from people who have used Bar's leak
several times with no adverse effects.  I think this is the exception and not
the rule.