Why does my Nissan Sunny overheat frequently? What are the possible causes and solutions?

The first thing to check is the radiator water—it might be low, or the water pump could be faulty. Also, if the cooling fan isn’t working properly or the thermostat is stuck, the car might overheat quickly.

I had the same issue with my Sunny, and it turned out that the radiator was clogged with mineral deposits. I replaced it and flushed the cooling system with proper coolant, and since then, the car has been fine.