How does a thermostat work?

Thermostats are a vital component of your vehicles cooling. They are the gatekeepers, the component that allows the flow of coolant through your engine and radiator. The component that decides when the coolant needs to pass through the radiator to cool down. 

Lets take a closer look at how a thermostat works in todays modern vehicles. Cooling systems are a sub system of todays modern automotive engines. As an engine functions, heat is created. 

This heat is created between the moving components inside of the engine. As well as through the heat generated during the combustion process. If this heat would be allowed to be absorbed into the engine. Eventually components would fail, or possibly even melt.

What is coolant?

To be able to combat these excessively high temperatures. The engine’s cooling system relies on a fluid known as “Coolant”. Coolant is a liquid that has many different properties that allow it to do its job at the best of its abilities. It is able to absorb the heat inside of the engine. 

As the coolant is circulated through the engine the heat is then released from the coolant through the radiator. Another important component of this sometimes misunderstood system. 

Along with the ability to absorb and release heat, coolant has many other important properties. 

Engineers have added different corrosion inhibitors, anti foaming agents, and even lubricants to create this super fluid.

These special properties are known better in the industry as additives.

How does a thermostat work?

The simple explanation. When the engine is warm it opens allowing coolant flow. When the engine is cold it prevents coolant flow which causes the engine to warm. 

If you are interested in the extended answer of how does a thermostat work, we need to take a closer look at the thermostat to understand its function. We can think of the thermostat as a sophisticated one way valve. 

By opening and closing this one way valve the thermostat can control the amount of coolant flowing through the engine. Inside of the thermostat is a special wax pellet. This wax pellet when headed begins to expand, when cooled the wax will than contract.

This expansion and contraction of the wax pellet is what causes the thermostat to open and close. When the engine is cold the wax pellet is contracted and does not open the thermostat. This allows the coolant to stay within the engine and to not flow through the cooling system. Resulting in the temperature of the coolant to increase.

Once the coolant temperature increases to between 195-220 F the wax pellet begins to melt. When the wax pellet melts it begins to expand which causes the thermostat to open. 

This opening of the thermostat allows coolant to flow through the cooling system. This results in the coolant that has absorbed the heat from the engine to flow through the cooling system to the radiator. 

Once the coolant passes through the radiator the coolant will release the heat to the atmosphere. Once the coolant releases the heat and cools down it continues to travel back into the engine. If the coolant is cool enough it will cause the belting to cool down which can cause it to close partially.

This opening and closing of the thermostat eventually balances out to where it maintains the proper operating temperature of the vehicle that it is equipped in.

As with any mechanical component on a vehicle a thermostat can and will fail given enough time. We have another amazing article located here, Common Symptoms of a faulty thermostat. This article goes through various types of symptoms that can be caused by a faulty thermostat.  

Its always important to understand how a thermostat works among other components on your vehicle. It will help you understand what is going on at all times, giving you the ability to communicate your vehicles issues with your local mechanic. Or possibly roll up your sleeves and attempt a repair on your own vehicle.

Staff Writer
Staff Writer
Our team of staff writers goes above and beyond in creating material that our readers love. They bring unique skills to the team that always provides a fresh perspective on the automotive industry.

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