My 1995 chevy Beretta keeps over heating but has great heat thermostat is good no leaks i dont think its the head gasket nor heater core relay fan only kicks on at 3/4 over heating point what. Could b

Its a 3.1 v6 engine

So what makes you think the thermostat is good? I lean toward the thermostat as it could be sticking, and bad. You having good heat tells me that there is no air pockets in the system. You may want to check compression since you see no leaks, as compression low on 1 or 2 cylinders would show potential head gasket also. Do you notice any white smoke coming out of the exhaust? Smell anything sweet?