I recently tried to change my coolant, and noticed that the bleed valve described in the owner's manual isn't there. There's a smooth hole in the top cover of the thermostat valve, with large diameter going to smaller diameter (presumably for the threads of the screw that's supposed to be there - no threads cut, though) and then a plug at the bottom. I took the cover off, and the plug looks like it is part of the cover casting, not simply a broken-off bleed screw.
Is this normal or maybe some sort of revision? If there's no bleeder there, where the heck do I bleed the cooling circuit? I'm tempted to just drill out the plug, tap the hole, and put a bolt in, but I figured I'd consult the experts

Thanks a lot guys! Appreciate the help...
-Johan