A Thermostat in My Car? Why Temperature Matters

When the outdoor temperature in the summer reaches eighty-five degrees or higher, you may adjust your home’s thermostat to keep the house cooler and more comfortable for your family. After all a thermostats job is to regulate temperature or activate another device, such as your air conditioner, when the temperature reaches a certain level. You may be surprised to know that most cars are equipped with a thermostat as part of the engine’s cooling system. While your home’s thermostat is used to monitor the interior of your home, your car’s thermostat is used to regulate the temperature of the engine to help the engine stay cool.

Most liquid-cooled engines are supplied with a thermostat, that measures about 2 inches in diameter, positioned between the engine and the radiator. Its job is to monitor the temperature of the engine’s coolant to precisely regulate the flow of coolant through the radiator, ensuring the engine operates at an optimal temperature.

An Integral Part of the Cooling System & How It Works

In addition to monitoring temperature, the thermostat is also tasked with blocking the flow of coolant to the radiator when the engine temperature is cold. until the engine is warm. When the engine is cold, coolant will not flow through the engine. As the temperature rises, however, the thermostat slowly begins to open. By the time the engine reaches approximately 200 degrees Fahrenheit, the thermostat will be open entirely. As the opening allows hot coolant in the engine to flow through the radiator, the water pump pushes lower temperature coolant from the radiator to the engine. By permitting the engine to warm up as quickly as possible, the thermostat aids in reducing engine wear, deposits, and releasing unnecessary emissions.

Thermostats are successful because of their effective design. They are a small cylinder, located on the engine side of the device, which is filled with a wax that slowly melts at approximately 180 degrees F, however, this can vary greatly from vehicle to vehicle. A rod, connected to the center of the valve, presses into the wax and when the wax melts, it expands pushing the rod out of the cylinder to open the valve and allow coolant to flow. The wax expands significantly because the wax is going from a solid to liquid state in addition to expanding from the heat. When the engine is shut off the process reverses to start all over again when the engine is restarted.

Common Problems

Most often when thermostats are failing one of two things has happened: the thermostat is either stuck in the open position or has stuck closed. Here’s how to tell if your vehicle’s thermostat is stuck in the open or closed position:

    • Stuck Open – when the thermostat is stuck in the open position, there is a continuous flow of coolant into the radiator, causing the engine to run cooler than recommended. That’s a good thing, right? Unfortunately, no. Overcooled engines actually run inefficiently resulting in an increase of fuel consumption, higher emission levels, and an increase of wear on engine components. Because the flow of coolant is constant, and the engine’s temperature is not reaching its suitable level, the engine may exhibit performance problems. Additionally, the heater may not heat properly, as the heater uses engine coolant to produce heat.
    • Stuck Closed – When the thermostat is stuck in this position, the circulation of coolant is blocked, entirely, preventing coolant from getting to the radiator to be cooled. This will result in extremely hot engine temperatures which will cause the vehicle to overheat.

Common Symptoms of Trouble

Thermostat replacements are a fairly inexpensive repair, when compared to the cost of replacing an engine, due to damage caused by excessive heat or repeated overheating. Here are three of the most common symptoms your vehicle may experience when a thermostat replacement is necessary:

    • Temperature Gauge Reads High or Engine Overheating – Within minutes of your engine running, you’ll notice the vehicle’s temperature gauge indicating the temperature is rising quickly and may go into the red zone of the gauge. This may be the first sign of a dysfunctional thermostat.
    • Temperature Changes Erratically – Temperature fluctuations, such as the gauge indicating the temperature is abnormally low to an immediate and unusual high can occur resulting in poor engine performance.
    • Coolant Leaks – Coolant leaks can be noticeable in several locations but are quite often found around the thermostat housing.

Though small, the thermostat is mighty. Ensuring the thermostat is working properly is vital to make sure your engine maintains the proper temperature to function. Don’t wait to have your vehicle inspected by a certified technician if it is indicating the engine is running too hot or too cold. Neglecting to address the symptoms that indicate your thermostat is under duress, could result in permanent damage to the engine which will result in costly and extensive repairs.