Understanding Thermostat Failure Modes

Most vehicles use surprisingly simple thermostats, but these devices serve a critical function in your engine's cooling system. Your thermostat acts as a valve that can control the flow of coolant through the system. As your vehicle warms up, the thermostat stays closed, preventing cold coolant from reaching the engine. Once the engine approaches operating temperature, it opens to avoid overheating.

Thermostats are a common failure point for many vehicles. When your thermostat fails, it can do so in ways that range from relatively minor to catastrophic. Recognizing these failure modes can help you avoid a potentially disastrous repair.

One Component, Two Failure Modes

Your thermostat's job isn't complicated: spring open when the engine is hot, and stay closed when it's cold. These two states also reveal the two common ways that a thermostat may fail. Thermostats typically stop working when they become stuck, which can happen while open, closed, or anywhere in between.

Manufacturers design their thermostats to fail in a safe or open position. Thermostats that fail open allow a steady stream of coolant into the engine from the moment you turn the car on, which prevents your motor from reaching its optimal temperature. Cold temperatures can cause your car to run poorly, burn more gas, and even accelerate wear on internal engine components.

While there are severe consequences to your thermostat sticking open, they pale in comparison to a thermostat that's stuck closed. In this case, the coolant won't flow through your engine at all, causing it to overheat rapidly. This situation can result in rapid engine damage, especially in warm temperatures or if you attempt to drive the car while your thermostat is stuck.

Thermostats rarely fail in the closed position, but it can happen, and it's critical to recognize the signs of overheating and act quickly.

What Should You Do?

While a closed thermostat is much more immediately dangerous to your vehicle, you shouldn't ignore problems in either case. A cold engine tends to run rich, which means your ECU will decide to dump more fuel into the combustion chamber than it can efficiently burn. The ultimate result is poor performance, reduced fuel efficiency, and incomplete combustion.

Incomplete combustion can be especially damaging to your vehicle. Excess fuel can damage your catalytic converters, ruining them in a relatively short amount of time. You'll also create more wear since the extra gas can wash away oil and reduce lubrication. While a cold condition might not instantly destroy your engine, it can create many expensive and frustrating problems.

In general, you should never ignore apparent symptoms of a thermostat failure or a thermostat check engine code. If your thermostat is stuck closed, you should stop driving your car immediately and tow it to a repair shop. While you may be able to drive a vehicle with a thermostat that's stuck open, you should still schedule a repair as soon as you can.

For more information on auto repair, contact a repair service in West Palm Beach, FL.