Fill and bleed the system. Pressure test(make sure it holds pressure). Run the vehicle and check fan operation, observe on/off temps w/scan tool(don't mess with a/c at this point). Drive the vehicle and observe coolant temp w/scan tool. Typically when engines overheat at cruise, it's a coolant flow issue. If they overheat in traffic, it's an airflow issue. You need to figure out exactly what's going on.