overheating!!!!
 

hello friends
here a small doubt that i come across during my recent trip

we are driving our 800 over hilly areas.After a breif driving of 5 km we come to know that our car[/b] is overheated and the main problem is with the sensor that start the radiator fan after 75 degree celcius but fails to do so. The engine[/b] got overheated and stops after some time. we only notice overheating only when car[/b] stop moving uphill and engine[/b] stop after some time.

My question is that is this a safety feature to shut[/b] down[/b] engine[/b] as soon as engine[/b] get overheaated or its a case of engine[/b]-seizure. i also found that the coolant moves to the reservior tank from the radiator . what is the main reason behind this all things