My son’s car ran hot a month ago and he said it lost power. Car was towed in radiator hose had came off they replaced that oil still looked good. The next day it ran hot again this time they replaced the thermostat. The next day the temp dropped from 175 to -40 while he was driving. On his way home from work it started overheating again an emergency message flashed on his dashboard engine light came on he pulled over and turned it off. Any suggestions as to what is causing this?