The only time my 91 Si gave me any overheating trouble was after it blew off a heater hose, empying the entire cooling system. I had overcooling trouble on mine as well, it's probably a common problem. The 4th gen Civic/CRX Si has a full width radiator, which is more than adequate for a beater 1.6/1.5L sohc. Ever notice that the newer civic's have a 1/2 length, but same width radiator(excluding b16 equipped).