Well, here is the plan. I am going to drill a small hole into the plastic
broken  bleeder screw. Then I am going to gently  drive  a  square cement
nail into this hole.Hey, its only plastic.Then I am gonna grip it with vice
grips and turn it out.Speaking of turns,turns out that the broken bleeder
valve screw is in the heater core proper, and not the on/off valve.So,I so
have more at stake in being successful here. Need the thread pitch before I
ectomize the screw.I checked my other core(parts van),and it seems that I
(forsomeunknownreason) forced a standard american bolt into this heater
core hole.Seems to me that I remember that it leaked after this. Dont know
why? I know that the core was a leaker before(not  from that hole though) ,
so no loss here. Any ideas about the bolt size or thread pitch. Thanks