Over heating how? Gauge? boiling over? Steaming? Need more good detailed info. Remember we are far, far away and can't see, hear, smell or touch it. There are many possibilities for over heating but need to narrow down before starting to list them all. Heater core plays no part in overheating, it's on a side circuit. Timing, bad thermostat, wrong thermostat, radiator, leaks, water pump, collapsed hose, BAD GAUGE OR SENDER, worn out rad cap, misfire, valves, clogged engine passages, fan clutch, fan, low oil, pulling heavy loads, slipping belt, broken belt, bugs..... well, I didn't list them all. Don't want ventilation around radiator, want tunnel effect.
