I am trying to remove my radiator and replace it with one from a 91 or 87 rx7 because mine is in terrible condition. I have a slight problem though. When I tried to drain it I couldnt get the screw off because its plastic and i guess no one ever drained the fluid because this thing just stripped right off. Now Im sure this has happened to someone else. Im not worried about salvaging the radiator and I bought a masondry drill bit. I was just thinking ill drill through then let it drain this way. Anyone have any better suggestions?

 

How about just taking the bottom radiator hose off?

 

Heat up a big flat screwdriver and press it into the plug, to melt a new slot into it that you can use.