I flushed/filled my coolant last weekend and had some problems with air in the system causing overheating and no heat. It appears that I've got the system bled and working well, but the last time I was trying to loosen the bleeder valve screw, it completely stripped. Even though it's still tightened, I don't like having the stripped screw in there in case I need to remove it in the future. I bought the replacement part from the dealer, but I can't figure out how to remove the stripped screw. I've tried putting epoxy in the hole and jamming a screwdriver in there, and that was pretty solid, but still didn't loosen the screw. I didn't think I tightened it too much, but apparently I did. Any good ideas to get this removed?