Your engine goes through a 4-stroke combustion cycle thousands of times each minute. This cycle generates an enormous amount of heat that threatens to damage the entire assembly. Temperatures can climb to the point where the engine overheats and the fuel within the combustion chambers begins to detonate. This can lead to damage to the pistons, valves, and rings.

Preventing this problem from happening is the cooling system. It is comprised of a network of components, including the radiator, hoses, water pump, and engine thermostat. Coolant flows through this network and into the engine, absorbing heat away from the assembly. It then transports that heat to the radiator, thus protecting your engine from overheating.

At the center of this system sits the thermostat. In this article, we'll take a closer look at the role it plays in the efficient operation of your vehicle. I'll also describe the consequences of this component failing, and offer a few suggestions for replacing it.

The Role Of The Thermostat

When you first start your car, the engine is cold. It requires time to reach its normal operating temperature. While the temperature surrounding the assembly climbs, coolant is kept from circulating through the cooling system. The component responsible for keeping it at bay is the thermostat.

One of the main purposes of the thermostat is to help your engine reach an optimal temperature as quickly as possible. That is when the assembly operates at its most efficient. Once a given temperature (typically 195 degrees Fahrenheit) is reached, the component opens and allows coolant to rush through the hoses toward your radiator. There, it releases heat and circles back to the engine to repeat the process.

What Happens When It Fails?

Even though this part is seldom mentioned, it has an important job to perform. If it fails to do its job, your engine can overheat. For example, the thermostat may remain in the closed position and thus, prevent coolant from flowing to the radiator. As a result, the heat contained in the fluid is not allowed to dissipate. Eventually, rising temperatures overwhelm your engine and cause it to seize. This can occur within minutes.

Suppose the component fails and remains in the open position. In this case, coolant is allowed to flow unhindered, which can cause the temperature surrounding your engine to drop. This, in turn, causes the operating efficiency of the assembly to falter. It should generate a fault code you can pull with a diagnostic scanner.

Replacing The Engine Thermostat

A failing thermostat needs to be replaced rather than repaired. Choose a replacement that has the same temperature rating as your failing unit. Most are set to open at 195 degrees Fahrenheit, but this can vary. Installing a replacement with the wrong setting can lead to excess fuel consumption, wearing around the rings, and other problems.

Most thermostats are located near the top radiator hose. Once you find this hose, detach and remove it. Have a small container ready to catch fluid as it leaks from the opening. You'll notice a few small bolts holding the component in place. Remove those bolts and lift the part from its housing.

Use a scraper to remove the residual gasket material around the exposed surface on the inside of the housing. Place a new gasket inside, install the new thermostat, and replace the top of the housing. Connect the top radiator hose, replace the clamp, and replenish the cooling system with coolant (use a 50-50 blend). This entire job should take less than an hour.

The thermostat's size and nondescript nature make it easy to ignore. But it plays a key role in the smooth operation of your engine. Even though it's a relatively inexpensive auto part (it can usually be purchased for less than ), it can cause expensive damage if it malfunctions.