if the head just snapped off sometimes theres a little of the + left on it and if your careful you can back it out with a sharp screw driver like a small flat blade, sometimes you can heat up a screwdriver point and push it into the remains of the plastic screw and back it out, if all else drill a hole in it and use a easy out. i've never seen a hole actually stripped out on the top of a bmw radiator the head pops off of the screw before you get enough torque on it
all america wants is cold beer warm cat and a place to take a poop with a door on it