With a new water pump, make sure there is no air in the system. This is confirmed by purging out all the air in the system, and there is nothing but coolant or radiator fluid in the cooling system. Air in the system can cause hot spots, which could then cause an overheating event. In any vehicle, operating temperature should be achieved within 15 to 20 minutes. This is during the summer or the winter. This is achieved in the winter by way of the thermostat, which restricts flow until operating temperature is reached. All components in the system must be operating as design, if not, the cooling system will have you replacing your engine.