Your engine is designed to run at a particular temperature. While it can operate safely within a fairly wide range, it provides the best power and efficiency when its operating temperature is just right. While it may be hard to believe, the component that plays the most important role in this vital task is the humble thermostat. Even on modern cars, thermostats are relatively simple devices. Despite their simplicity, however, they can have a major impact on how well your engine runs. Although rare, it's even possible for a failed thermostat to potentially lead to serious engine damage! Keep reading to discover how these basic devices work and why it is so important that yours is operating properly.

What is a Thermostat?

Just like the thermostats in your home, the thermostat in your car is responsible for maintaining a particular temperature. When the engine is too cold, the thermostat prevents coolant from entering the block. Although no coolant flows through the thermostat, the engine's temperature is not completely unregulated as some basic cooling is provided both by the air moving through your engine bay and by the oil inside of your engine. Once a particular internal engine temperature is reached, the thermostat opens up to allow coolant into the block. The circulation of coolant between the engine and radiator is what keeps your engine operating at its peak temperature.

How do Thermostats Work?

Just how simple are thermostats? On most cars, thermostats are simply valves controlled by wax. The wax is located on the side of the thermostat facing the engine. As the wax heats, it melts and expands, which causes the valve to open. As the wax cools, it contracts and a spring forces the valve closed. A few modern manufacturers now use electronically controlled thermostats, but these devices still operate in a similar way. The primary difference is that the temperature of the wax is not controlled by the engine, but by an electronically controlled heater coiler.

The Consequences of Thermostat Failure

It should be obvious that there are really only two possible outcomes if a thermostat has failed: your engine will run too cold or your engine will run too hot. Which one actually happens will depend on whether your thermostat fails in the open position or in the closed position. Luckily, thermostats are generally designed to fail open, meaning that they will allow coolant to flow regardless of engine temperature. This can cause an engine to take too long to get up to normal operating temperature and can even prevent the engine from getting there at all. Thermostats that are stuck closed are fortunately less common, but they can quickly result in your engine overheating.

The Consequences of an Open Thermostat

While a thermostat that is stuck closed is obviously catastrophic, an open thermostat is damaging as well. If your car is unable to reach its proper operating temperature, then your fuel economy will suffer and you will likely notice other drivability symptoms such as poor performance or rough idling. It can even result in internal damage over time since the computer may remain in its initial open loop state, resulting in a rich fuel mixture. Modern cars will usually throw a code (and illuminate a check engine light) if the thermostat fails, so it pays to have the problem fixed as soon as you notice it.

To learn more, contact an auto repair shop near you.