Engine is overheating

I purged any air out of the system, refilled coolant, ran the engine. The heater still is not workinging and the car is still overheating

I have a 1995 sentra 1.6 engine. It was overheating faulty thermostat, I tested, I changed it. New thermostat same thing after one hour driving radiator fan on all the time, driver side of radiator not as hot as other side. Check temperature with computer it says that the car overheats changed thermostat the same thing happens after about an hour of driving the electric fan does not stop turning until I turn off the motor. Changed the water temperature sensor also. Driver, s side of radiator not as hot as other side. Purged the coolant also. Checked the water temperature with a computer hook up that I have it says water 82c degrees Celsius, new thermostat is 180f degrees other people says it should be 170f degrees, but I don, t think that account for the radiator not been hot on the two sides. Have 300,000 kilometers. Taken good care of it. Last year changed water heater core. Old thermostat would not open tested with boiling water it stay lock.A few months ago check compression it was still okey. Sometimes at idle I can hear like one of the injectors is off a little bit, as it runs I can count from one to four and it sounds a bit off, this has been going on for a long time.