In PAKISTAN most of the cars having problem that their radiator fan starts directly when the car is started regardless of the water temperature in the radiator, because the fan (electrically driven) circuit is by passed from the thermostat switch.
 

In rare wheel drive cars the radiator fan is not electrically driven but it is belt driven. It starts running as soon as the engine is started. To keep the engine temperature at optimum level the water is not allowed to circulate (when cold) in the radiator as the THERMOSTAT VALVE remains closed. As soon as the temperature starts to rise the valve is opened and the belt driven fan keeps the air circulating making the water temperature stick to an optimum level.

The following are the problems keeping in mind that if engine is not running on its normal working temperature.

• It will decrease the air/petrol mixing efficiency.

   

•  It will effect the distribution of petrol/air mixture to each cylinder.

   

•  This will decrease the volumetric efficiency of the engine resulting in increased fuel consumption.

   

•  The engine oil will get fouled prematurely resulting in more oil changes.

   

•  The fouled engine oil will result in the premature engine wear shortening the engine life.

   

•  Engine will never give its full power and torque.