it takes quite a while idleing for air to purge out of the heater core even with heat on full. takes less time with water during flushing, than 50/50/ antifreeze during the final fill. more viscous i guess. eventually your heat should work when the air is purged. the engine coolant drain cock is 10mm and vertically oriented, right by the oil drain pan. mine was a little rusty but didnt break, i sprayed it first and waited 24 hours. just do not overtighten it