Welcome to JA.
First check and make sure the cooling fan is operating properly. Then next check the radiator for hot spots to see if it may be clogged. It is best to check it with an infared thermometer. Check the temp of it from bottom to top and it should get cooler on the way up if you have any excessively hot spots then it is clogged. Also make sure all of the air is purged out of the coolant system.