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It is part of the control system of the car. If the temperature is too low, you lose efficiency. If it is too high, you get engine damage, knocking, etc.

So the thermostat will give feedback to the water pump to control the rate at which coolant flows through the engine block and radiator. It can also provide feedback to the fuel injection system to regulate the amount of fuel and air that goes into the engine, and to the temperature indicator on the dash.

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Its a valve. It is located in the cooling circuit, between the engine and the radiator. If it opens it allows flow of water, assisted by a water pump, to take place from the block to the radiator in order to allow the block to "give up" excessive heat.

It is a self regulating device and it is calibrated to open at a particular temperature - usually about 95 degrees C. It has a hysteresis also, that is a gap between the open and close temperature due to mechanical friction within the device itself and therefore after cooling has taken place it may not close again until the temperature drops to 90 degrees C - a hysteresis of 5 degrees C.

So in this example, when the engine gets to temperature, it should maintain an operating temperature of between 90-95 degrees C.

Why is this important? It is critical for a couple of reasons, firstly the many machined limits and fits of critical moving parts are designed with the prescribed operating temperature in mind. Secondly, and maybe more critically, the lubricating oil viscosity is too thick at low temps and too thin at higher temps. Oil breaks down rapidly when subject to too high a temp and closely machined mechanical parts experience boundary lubrication - that is metal to metal contact.

Probably the best way to screw up your engine is to allow it to overheat!


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The thermostat regulates the temperature of the engine.

When it is fully open the coolant flows from the engine block to the radiator and to maintain temperature when its closed the circuit to the radiator is off. It's usually located in the upper section of the engine block

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thermostate means thermo=heat.state=phase i.e we can say that it convert heat from 1 level to another level because after a long run of engine it definite goes to heat but for cooling medium is required that is water or air or any thing else so for this medium a container is required that is nothing thermostat iu used

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Without a thermostat, the engine block would swell and shrink as the temperature varies with load. This would make the pistons wear quickly and irregularly. Ever notice how an engine is somewhat noisier when it is cold that when it is at operating temperature?

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