Understanding Your Thermostat

This is the norm: A car comes into Nigeria, we take it to a mechanic for evaluation and they tell us to remove the thermostat.
Why??? Because it is not ideal for our climate and could cause overheating of the engine. I once heard a mechanic tell someone it just doesn’t do anything. The next thing they do is to make the fans run permanently, again, to prevent overheating. THIS IS VERY WRONG!!!

The combustion process in a car is optimized at an average temperature of 90◦C. Parts of the engine could get damaged if the temperature exceeds the required range by a large degree (this is overheating) and the car will not optimize the combustion process if the temperature is lower than the required range by a large degree. The car knows this and so it always tries to limit the engine temperature to that range and it uses a couple of devices and processes to do this. The main one is the thermostat.
We all know that the car uses coolant to cool the engine by allowing it flow through the water lines in the engine. When the car is started in the mornings or after sitting for a long time, the engine is usually relatively cold. Since the car knows the combustion process is not optimized at that point, it then uses the thermostat to stop the flow of the coolant through the engine. This will cause the engine to heat up to the desired temperature quickly. The thermostat then gradually opens to allow the flow of the coolant as the temperature reaches 90◦C (this is usually when the needle is at the middle of the temperature gauge).

What generally happens when the thermostat is removed is that the coolant is always flowing and the car then looks at other ways of trying to get hot. It then increases the engine speed at idle and while moving, delays the changing of gears in an automatic transmission (in some cars it even prevents it from entering the final gear), makes use of the EGR... All these things consume more fuel and are all meant to stop when the engine reaches 90◦C. Since it never reaches that temperature without the thermostat there, all these processes continue as long as the engine is on.

Yes, thermostats can go bad over time. When this happens, replace them instead of throwing them away. Most of the time, thermostats themselves are not the reason for cars overheating. A leak in the water system is the number one cause of overheating. An easy but unreliable way to know if the thermostat of a car is faulty is to check the hose that enters the radiator and the one that leaves the radiator when the car overheats. If one is relatively cold while the other is relatively hot, then the thermostat is most likely faulty. If they are both relatively hot, then the thermostat is good. Note that overheating is not when the temperature gauge is at the middle. THAT IS THE PERFECT PLACE FOR IT TO BE.

So we have learnt that removal of the thermostat of a car can cause the car to keep pouring excess petrol into the engine, raise the speed of the engine higher than normal, affect the way the transmission shifts, prevent the transmission from entering overdrive. Does not sound good right?