These engines overheat very easily, just one cupful of coolant missing is enough to airlock the cooling system. It needs to be bled from the rear bleed point only, it can't be done from the radiator cap.
My coolant bypass kit gets rid of most of the common airlock issues, and replaces that stupid plastic bleed point with a custom alloy part incorporating a ball valve. Makes for a one fill cooling system by allowing the air trapped in the block to escape easily. It also increases the flow of coolant by 50%.