If your truck's coolant temperature gauge rises rapidly into the red zone while hauling a heavy load, what is the best immediate action?

1. Turn off the engine immediately while coasting downhill
2. Pull over safely, let the engine idle for a few minutes to cool down, and check for coolant leaks and fan belt condition
3. Pour cold water directly onto the hot engine block to cool it down
4. Increase speed to force more air through the radiator grill