Internal combustion engines are like the porridge in “Goldilocks and The Three Bears” – they need to be at just the right temperature, neither too hot nor too cold, and the device that ensures this is called the engine thermostat. But what if your engine is always running cold? Can this harm the engine? What causes it, and how can you fix it? Let’s dive into these questions and find out more about the ideal operating temperature for engines.
What is the ideal temperature for a car engine?
Many people, especially those not too keen on car mechanics, may only worry about engines overheating. We’re all familiar with the dangers of an engine running too hot, but an engine running too cold is also a problem. Engines have an optimal operating temperature, usually around 200°F (93.33°C), though this can vary. Some operate best near 100°C, while others function at lower temperatures.
Why is the 100°C mark significant? It’s because this is the boiling point of water, a key component in engine coolant. While most engines can handle temperatures above 100°C without immediate damage, consistently high temperatures are not advisable. It’s important to maintain your engine within its ideal temperature range for optimal performance and longevity.
How does a car maintain temperature?
Every engine is designed to operate within a specific temperature range, which is important because the materials and internal clearances of the engine are optimized for a certain operating temperature. If the engine runs colder than intended, these tolerances can be adversely affected.
To maintain the engine within this critical temperature range, a component known as the thermostat is used. The thermostat is a vital part of the engine’s cooling system. This system circulates a coolant – typically a mix of antifreeze and distilled water – through the engine block with the help of a water pump. The coolant absorbs heat from the engine and then releases it through the radiator.
If the coolant were to circulate continuously, the engine would never reach the optimal operating temperature. This is where the thermostat comes in. It controls the flow of coolant, ensuring the engine heats up quickly and maintains the ideal temperature for efficient operation.
What is an engine thermostat?
As previously explained, a thermostat is a heat-activated valve in the engine’s cooling system. It opens to allow coolant circulation through the system once the coolant reaches a certain temperature. Until it reaches this temperature, the thermostat remains closed, preventing the coolant from circulating out of the engine.
It’s important to note that a failing thermostat can be a serious issue. Luckily, most thermostats are designed to fail in the open position, thanks to a safety feature. This design prevents the more severe consequences of a thermostat failure, like engine overheating, blown head gaskets, or warped cylinder heads, which would be more likely if the thermostat failed in the closed position.
What are the symptoms of a bad thermostat?
A thermostat is a straightforward component, making it relatively easy to spot signs when it starts to fail. Here are a couple of common symptoms:
- Car Overheating: One serious sign of a failing thermostat is the engine overheating. If you find yourself in this situation, turn your car’s heater to the highest setting to help draw some heat away from the engine, and pull over as soon as it’s safe to do so.
- Erratic Temperature Gauge Readings: Another symptom is erratic movements of the temperature gauge needle. This happens when the thermostat gets stuck in the open position. When your car is idle, the engine heats up because there’s no cold air flowing through the radiator. But once you start driving, the engine begins to cool down again due to the airflow.
These are the main indicators of a problematic thermostat. It’s crucial to address these issues promptly. Even though it might seem okay to drive with a thermostat stuck in the open position, it’s really not recommended because it can lead to further engine issues.
How do you test a car thermostat?
The most effective method to test a thermostat is by removing it from the vehicle. Being a temperature-sensitive valve, you can check its function by placing it in a pot of boiling water. Watch to see if it opens when the water reaches about 200°F. If it does, the thermostat is functioning correctly. However, if it stays closed or is already closed and doesn’t open, then it’s time to replace it.
When it comes to testing the thermostat without removing it from the car, your options are limited. If your vehicle is overheating, you can try to assess the thermostat by feeling the temperature of the lower radiator hose. If this hose is cold while the upper hose is hot, it’s likely that your thermostat is stuck in the closed position. In this case, it’s not safe to drive the car, as you risk serious overheating damage.
How Long Can an Engine Run Cold and is it bad?
Answering this question isn’t straightforward. Most automotive experts agree that it’s not ideal for an engine to operate outside its optimal temperature range for an extended period. However, driving a cold engine short distances, like to a mechanic’s shop, won’t immediately result in catastrophic engine damage.
The real problems begin when you consistently ignore the issue and keep using the car for weeks or months under these conditions.
The primary concern is that an engine running cold will wear out more quickly. But there’s more to it in modern cars, where the cooling system is integrated with the Engine Control Unit (ECU). The ECU adjusts the fuel mixture to be richer when the engine is cold to help it warm up faster.
Consistently running a cold engine can lead to increased fuel consumption. It also often results in more carbon buildup in various engine parts. The most harmful effect is when this rich fuel mixture leads to unburned fuel entering the exhaust system. This is particularly problematic for the catalytic converter, where the excess fuel can cause significant damage.
Can I replace a car thermostat myself?
Replacing the thermostat in your car can range from easy to challenging, depending mainly on the make and model of the vehicle. On older cars, where thermostats are independent units attached directly to the engine, the process is relatively straightforward. You just need to detach the hoses connected to the engine and remove the faulty thermostat.
However, the situation is different with many modern European cars. In these vehicles, thermostats are often integrated into the water pump or hoses. This integration can make the replacement more complex for those who like to do car repairs themselves. While it’s not an impossible task, it certainly requires more effort and knowledge compared to the simpler setup in older cars.
How do you replace a car thermostat?
Replacing a car thermostat is a task that can be done by someone with basic mechanical skills, but it’s important to follow the correct steps and take necessary precautions. Here’s a general guide:
- Prepare the Vehicle:
- Ensure the engine is cool before you begin.
- Park the car on a level surface and engage the parking brake.
- Disconnect the battery to prevent any electrical accidents.
- If Necessary Drain the Coolant:
- Place a container under the radiator and open the drain plug to catch the coolant. Remember to properly dispose of or recycle the old coolant.
- Locate the Thermostat:
- Find the thermostat housing. It’s usually attached to the engine block and connected to the top radiator hose.
- Remove the Thermostat Housing:
- Loosen the clamps and remove the radiator hose from the thermostat housing.
- Unscrew the bolts holding the thermostat housing to the engine. Be careful as some coolant may still be inside.
- Remove the Old Thermostat:
- Take out the old thermostat from the housing. Pay attention to its orientation for correct installation of the new one.
- Clean the Housing Surface:
- Clean any old gasket material and residue from the thermostat housing and the surface it mounts to on the engine.
- Install the New Thermostat:
- Place the new thermostat in the housing in the same orientation as the old one.
- If needed, install a new gasket or apply gasket sealant as per the manufacturer’s instructions.
- Reassemble the Housing and Hoses:
- Reattach the thermostat housing to the engine and tighten the bolts.
- Reconnect the radiator hose and secure the clamp.
- Refill the Coolant:
- Refill the cooling system with coolant. Make sure to use the type recommended by your vehicle manufacturer.
- Bleed the Cooling System:
- Start the engine and let it run with the heater on max. Check for leaks and let the air escape from the cooling system. This might involve opening a bleed valve if your car has one.
- Check for Proper Operation:
- Monitor the temperature gauge to ensure the thermostat is working correctly.
Remember, these steps are a general guide and can vary depending on the vehicle. Always refer to your vehicle’s service manual for specific instructions and torque specifications, we recommend Haynes. If you’re not comfortable performing this task, it’s best to have a professional mechanic do it.