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Is Your Car Overheating from a Failing Thermostat - How to Tell

Is Your Car Overheating from a Failing Thermostat - How to Tell | Mancinelli's Auto Repair Center

One of the most common causes of engine overheating, a frustrating and potentially damaging issue, is a failed thermostat. But how can you be certain that this is the problem? Let's examine the symptoms of a failed thermostat and find out.

What Does a Car Thermostat Do?

First things first, what exactly does a car thermostat do? The thermostat is a small but vital component of your car's cooling system. Its primary function is to regulate the coolant flow between the engine and the radiator. When you start your car, the thermostat is closed, allowing the engine to warm up quickly. Once the engine reaches its optimal operating temperature, the thermostat opens to let the coolant flow through the radiator, preventing the engine from overheating.

Without a functioning thermostat, your engine can either overheat because the coolant isn't circulating properly, or it can take too long to reach the proper operating temperature, which can also cause engine problems over time.

Signs of a Failing Thermostat

How can you tell if your thermostat is the root of your overheating issues? Here are some common signs to watch out for:

Erratic Temperature Gauge
If you notice the temperature gauge fluctuating between hot and cold, it could be a sign that your thermostat is stuck open or closed.

Overheating Engine
The most obvious sign is your engine overheating. If the thermostat is stuck closed, the coolant can't circulate, causing the engine temperature to rise.

Coolant Leaks
A stuck thermostat can cause the coolant to boil over, leading to leaks around the thermostat housing or other parts of the cooling system.

Heater Issues
If your car's heater isn't working correctly, it might be because the thermostat is stuck open, preventing the engine from reaching the proper temperature to provide heat.

Why Does a Thermostat Fail?

Thermostats can fail for various reasons, and understanding these can help you prevent future issues. The most common reasons include:

Wear and Tear
Like any mechanical part, thermostats can wear out over time. The constant opening and closing can eventually cause the part to fail.

Corrosion and Deposits
Coolant contains additives to prevent corrosion, but over time, deposits can build up and cause the thermostat to stick.

Coolant Issues
Using the wrong type of coolant or not changing it regularly can lead to thermostat failure. Always follow your manufacturer's recommendations for coolant type and change intervals.

How to Address a Malfunctioning Thermostat

If you suspect your thermostat has failed, it's crucial to address the issue promptly to avoid engine damage. Here's what you can do:

  • Check the Coolant Levels: Before jumping to conclusions, check your coolant levels. Low coolant can also cause overheating.
  • Inspect for Leaks: Look for signs of coolant leaks around the thermostat housing and other parts of the cooling system.
  • Consult a Professional: If you're not comfortable diagnosing or fixing the issue yourself, it's best to take your car to Mancinelli's Auto Repair Center. We can perform tests to confirm whether the thermostat is the problem and replace it if necessary.

Preventing Future Thermostat Failures

While some thermostat failures are unavoidable, there are steps you can take to minimize the risk:

Regular Maintenance
Regularly checking and maintaining your car's cooling system can help prevent thermostat issues. This includes checking coolant levels and changing the coolant according to your car manufacturer's recommendations.

Use the Right Coolant
Always use the coolant recommended by your car's manufacturer. Different coolants have different properties, and using the wrong type can cause deposits and corrosion.

Flush the Cooling System
Periodically flushing your car's cooling system can remove deposits and prevent buildup that can cause the thermostat to stick.


Is your car overheating? Let the experts at Mancinelli's Auto Repair Center diagnose and fix the issue before it leads to costly repairs.

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