Started out as simple tstat replacement. One of the easiest jobs I've done on this car.........or so I thought. When I was bleeding the system, I went to tighten,(or overtighten), the vent screw on the overflow tank and I snapped the screw head off. Problem is by time I finally worked the screw free,[accidently drilled through it in the process(I know stupid)], approx. 10 to 15% of the screw had fallen into the tank. What do I do now? I'm sure if I run it as is I am just asking for other issues due to blockage from the screw remnants. Can I seperate the tank from the radiator w/out damage, how can I be sure I get all and not just most of the pieces ? By the way its an M20. If anyone has any experience/ideas on my self-made catastrophy I'd appreciate the wisdom.

WARNING, to anyone who reads this post and doen't know better. Do NOT over torque plastic vent screw!!!