My 2004 sienna overheats and everybody tells me it is a different thing,it leaks water and mechanics said it's the radiator,it's the water pump,it's the thermostat,how can you tell what it is.?
What you need to do is pressure test the cooling system, that will show leaks. What does happen is you get a leak, and do not notice it, then you develop another one or two, and when you fix the first issue, OTHER leaks show up. << Common thing.
Pressure test, if the rad leaks, replace it, pressure test again, repair what shows up, if anything...You need to be able to hold pressure to keep from overheating. It works like a pressure cooker, you can exceed boiling point with pressure.
This is why you should NEVER open a hot cooling system, it often will violently overheat when pressure is released.