Just a guess based off the limited information provided, but I would first check your radiator fan to see if it is working or connected properly. I would also check the coolant level in the coolant reserve tank, because you may need to top it off.
Turn all of your heaters(front and rear) to the high setting while at idling to get a proper coolant level reading since coolant is used by the heater cores.
What is 1:00? I assume the red zone.
Why did you change the radiator in the first place if the engine was not overheating?