Kept having a coolant leak at the T with filler screw...put in new gasket and still had leak. When I tried tightening the bolts down to get a better seal, the top bolt completely stripped out. After a little cussing and a busted knuckle, I found the problem:
Yeah, metal shavings and threads are FUBARed.
Considered trying to tap it for some new threads, but would rather just throw in a new one if it's not prohibitively expensive.