Tap up on the bottom while trying to turn it, if it doesn't turn, Unscrew it from the radiator.
or as @PoTreeBoy said remove the lower radiator hose to drain it.
Tap up on the bottom while trying to turn it, if it doesn't turn, Unscrew it from the radiator.
or as @PoTreeBoy said remove the lower radiator hose to drain it.