>So maybe a new engine PLUS a new $350 or more radiator?  Any possible fixes
>for this without replacing the radiator?
>

YES, drain the coolant and do this:  take the hoses off the rad, and take
the rad out and then somehow get the screw out, drill it out what ever, NOW
go to a plumbing store and get the smallest valve that you can find and
replace that whole thing with the valve. so when you need to bleed, you can
open the valve and close it easily, instead of having to screw a screw into
a hole while coolant is pouring out.