replace engine? or fix crack?
 

i have a 93 gs 300 recently its been acting crazy, i thinkh its a cracked head gasket when i start it starts boiling over in the resevoir and gets real hot but its not showing it on the reader, i also recently rplaced the thermostat, radiator and the crank shaft pulley, do you think its a crack, and would it be cheaper to replace it w a whole new engine, or to fix the crack in the head?