Causes of Thermostat Failure
The main function of a car thermostat is to regulate the flow of coolant to maintain optimal engine temperature. When you start your car after it has been sitting for a while, the thermostat remains closed, allowing the engine to warm up quickly by preventing coolant from circulating through the radiator.
As you continue to drive, the engine temperature rises, causing the thermostat to open once it reaches its predetermined temperature (usually around 195°F to 220°F). This allows coolant to flow through the radiator, where it is cooled before returning to the engine to absorb more heat.
The thermostat constantly adjusts its open/closed position based on the engine’s temperature, maintaining a balance between the hot coolant coming from the engine and the cooled coolant returning from the radiator. This process helps keep the engine operating at its optimal temperature range, typically around the midpoint of the temperature gauge.
If you leave your car idling for an extended period, the thermostat may remain closed, as it takes longer for the engine to reach its operating temperature when not under load. However, once you start driving and the engine works harder, the thermostat will open to prevent overheating.
The thermostat’s operation is controlled by a temperature-sensitive element, such as a wax pellet or a bimetallic strip, which expands or contracts in response to changes in coolant temperature. As the element expands, it opens a valve within the thermostat, allowing coolant to flow through. When the coolant temperature drops, the element contracts, closing the valve and restricting coolant flow.
In addition to the thermostat itself, a coolant temperature sensor provides input to the vehicle’s engine control module (ECM), which monitors and regulates various engine functions. This sensor helps the ECM determine when to adjust the fuel injection, ignition timing, and other parameters to maintain optimal performance and fuel efficiency.
Environmental factors, such as outside air temperature, can also influence the thermostat’s operation. However, a properly functioning thermostat should be able to adapt to these conditions and maintain the engine’s operating temperature within the desired range.
1. Age and Wear – A car thermostat won’t last forever. Constant exposure to temperature changes and repetitive motion can cause the thermostat to wear out over time.
2. Coolant Contamination – Dirty or acidic coolant can clog or corrode the thermostat, causing it to stick or malfunction.
3. Overheating – Frequent engine overheating puts additional stress on the thermostat, potentially causing warping or premature failure.
4. Incorrect Installation – Installing the thermostat upside down or overtightening the housing can lead to improper functioning or damage.
5. Manufacturing Defects – In some cases (usually with cheap aftermarket brands), a faulty thermostat may be caused by poor construction or subpar materials. Sticking with OEM parts reduces this risk.
6. Impact Damage – Depending on where the thermostat is located, physical damage to the thermostat housing or surrounding components from road debris or accidents can cause thermostat failure.
Preventive Maintenance
Performing regular preventive maintenance of your vehicle’s cooling system is more important than most car owners think. Here are a few things you can do to extend the life of your thermostat and avoid costly engine repairs due to overheating.
Regular Coolant Flushes
Over time, coolant can become contaminated with rust, debris, and other particles that can clog or damage the thermostat. Flushing the cooling system and replacing the coolant at the intervals recommended by your vehicle’s manufacturer helps maintain the health of your thermostat and other cooling system components.
Consult your owner’s manual or a trusted mechanic to determine the appropriate schedule for your vehicle. The cost of a coolant flush is only slightly more than what many people spend on an oil change. A DIY radiator flush is also very doable for many individuals who want to save some money.
Thermostat Inspection
Whenever you have your coolant flushed professionally, ask your mechanic to inspect the thermostat for any signs of wear, damage, or malfunction. A good repair shop will often automatically do this.
They can check for leaks, corrosion, or sticking, and recommend replacement if necessary. Catching thermostat issues early can prevent more serious and expensive problems down the road.
Fix Coolant Leaks ASAP
If you notice any coolant leaks, have them repaired as soon as possible. Low coolant levels can cause the engine to overheat, putting additional stress on the thermostat and other cooling system components.
Regularly inspect your vehicle for signs of coolant leaks. While a small puddle is easily noticeable, sometimes coolant loss isn’t so obvious.
Monitor Engine Temperature
Pay attention to your vehicle’s temperature gauge while driving. If you notice the gauge consistently reading higher or lower than normal, or if the engine overheats frequently, have your cooling system inspected by a professional.
There’s no better person to catch a thermostat issue early on than the person who regularly drives the car. If you get into the habit of glancing at the temp gauge during your drives, a small change will often be apparent.
Use the Right Coolant
Always use the type of coolant specified by your vehicle’s manufacturer. Don’t just simply buy a yellow jug of Prestone because that’s what your dad taught you 20+ years ago. As vehicles have become more sophisticated, different manufacturers call for different types of coolant.
Using the wrong coolant or mixing different types can cause corrosion and damage to the thermostat and other cooling system parts. If you’re unsure about which coolant to use, consult your owner’s manual.
Keeping the Radiator Clean
A dirty or clogged radiator can reduce its ability to efficiently cool the engine, putting additional strain on the thermostat. Periodically clean any debris from the front of the radiator, such as leaves or insects, to make sure it gets proper airflow.
