i suggest removing all the frost plugs and flush everything out. i have in certain instances to clean up some water passages used liquid drano. pull all the hoses off the radiator and heater core before filling the system. plug off the lower rad hose and both heater hoses and fill the system with a solution of drano and water and let it sit for a good half hour then flush the system completely with fresh water the longer the better as you dont want any of the drano left in the system. call me crazy but iam not the only mechanic that has done this. its beginning to become a common pratice for cleaning out the newer vehicle heater cores up here in the north country. later MO
