Symptoms of a Faulty Thermostat

Symptoms of a Faulty Thermostat – Several significant components make up the engine and the thermostat is one of them. 

The engine works at high speed and generates a lot of heat which can lead to complications if not regulated. This is why every car has a thermostat to monitor and control the flow of coolant in the engine. 

Thermostats help to reduce the temperature of the engine anytime it heats up. It also helps to prevent overheating. As a crucial component of a car’s cooling system, the thermostat must always remain in good working condition.

What is a Car Thermostat?

The thermostat is a small component in your engine’s cooling system that regulates the circulation of coolant in the radiator and the engine. The thermostat has a diameter of about 5cm and it is positioned between the engine and the radiator in the hood.

The thermostat serves as a temperature control mechanism in your car’s cooling system. It monitors the temperature of the coolant, controls the amount of coolant that is sent to the engine, and controls when the radiator should send the coolant to the engine.

How Does the Thermostat Work?

The working principle of a thermostat is not as complex as some other components could be. The thermostat is a small valve mounted between the engine and radiator. 

The thermostat opens when the coolant in the engine gets too hot in order to send the hot coolant to the radiator for cooling. If the coolant is not hot, the thermostat remains close and allows it to continue circulating in the engine.

The thermostat restricts coolant from getting to the radiator until the engine warms up to a certain temperature, about 200°F or 95°C. When the engine’s temperature gets to this point, the valve opens and circulates coolant to prevent overheating. The thermostat is at a closed position when the engine has not generated any heat.

The thermostat knows when to open and close because a kind of wax is present, and it serves as an expanding agent. When the temperature or heat in the engine gets high, the wax expands and opens the valve, when the temperature is normal, the wax shrinks and returns the thermostat to the closed position.

Functions of the Thermostat

The thermostat plays a very vital role in the engine’s cooling system. 

Here are some basic functions of a thermostat in your car. 

  1. It regulates the amount of coolant that moves between the engine and the radiator. That is the amount that is sent to the radiator and what is recirculated back to the engine.
  2. The thermostat prevents overheating, monitors, and controls engine temperature by sending coolant to the engine when it is due.
  3. Thermostats preserve the engine’s life by maintaining a good operating temperature always.

Types of Thermostats

Car thermostats are divided into two major types.

Thermostat without a bypass valve 

This type of thermostat is very common in old car models. 

It is located on the radiator inlet and does not come with a safety line that can allow coolant flow if there is an issue with the thermostat. 

When the car engine is cold, coolant/water will be trapped in the radiator and water jacket.

One good thing about thermostats without a bypass valve is that they are very affordable, but they are not very safe to use because they have no safety lines.

Thermostat with bypass valve

This type of thermostat is located on the radiator outlet with a valve that is integrated into the thermostat. 

They are common in recently manufactured cars. It permits water to flow from the water jacket to the thermostat and to the pump which sends it back to the water jacket. 

The bypass valve does not allow water to get to the radiator, rather it helps circulate the water around the cylinder block to enable the engine to get to its normal operating temperature quickly.

This type of thermostat has a safety line and in case of any damage to the thermostat, it will help in cooling the engine’s temperature. Also, this type of thermostat is very effective but are highly priced.

Symptoms of a Faulty Thermostat and its Causes

The thermostat is responsible for regulating the temperature of your engine and its failure will pose a threat to the efficiency of your engine. 

The thermostat must remain in good form to avoid problems with your engine and the overall performance of your car. 

Here are indicators of a failing thermostat.

Coolant leak

Coolant leaking from your engine is one of the major symptoms of a faulty thermostat.

Coolant keeps the engine at its right operating temperature and if it is leaking, there will be a problem. 

One reason for this leakage is due to a faulty thermostat being stuck closed and will not open for the coolant to flow to where it is supposed to, like to the radiator. So, when the coolant heats up and the pressure gets too high, it will force an escape through any weak point since it can no longer get to the radiator.

Unusual temperature changes inside your car

A faulty thermostat can cause the temperature inside your cabin to rise and drop all of a sudden. 

Coolant helps to cool down the heat inside your car and if the thermostat fails in performing its function by ensuring a steady temperature inside your car, there will be fluctuations in temperature.

Noise from the engine

You will experience a boiling or knocking sound emanating from the radiator or engine if there is an issue with your thermostat. This noise occurs as a result of coolant boiling in the system due to a stuck valve.

Engine overheating

An overheated engine can lead to fatal issues in your vehicle. 

A faulty thermostat will restrict coolant from flowing to the engine and radiator as it should which causes overheating. The hot coolant is supposed to flow from the engine to the radiator to cool down before returning to the engine. However, a stuck closed thermostat will restrict this process which will cause the engine to overheat.

Engine fails to reach the operating temperature

A thermostat that is stuck open will prevent the engine from reaching its normal operating temperature. 

This is because coolant is flowing freely from the radiator to the engine and the thermostat valve does not close to allow some coolant to remain in the engine to get hot and warm up the engine before flowing to the radiator. This means that the valve stays open when it’s supposed to be closed.

Heater malfunction

If the thermostat is stuck in an open position, the heater will malfunction because the coolant will constantly flow into the engine even when it is not needed. 

At this point, if you turn your car’s heater on, it’s cool air that will be coming out from the HVAC no matter how much you increase the heater temperature.

Reduced engine performance

A faulty thermostat will affect your engine’s performance. 

If the thermostat is stuck open or closed, it will make your engine too cool or overheated. It will also affect the efficiency of the engine because the engine is supposed to run at a temperature of 90°C to 140°C.

Effects of Driving a Car without a Thermostat

After assessing the functions of a thermostat in your car, driving your car without it unarguably comes with lots of consequences.

Some of such consequences include:

Poor car efficiency

Driving without a thermostat reduces the performance of a car. This is because the thermostat helps to regulate the temperature of your car by controlling the flow of coolant from the radiator to the engine and vice versa. 

If there is no thermostat, your engine temperature will be as low as 50°C which will affect the performance of your car.

Worn-out engine parts

Running a car without a thermostat will cause parts like the head gaskets, hose pipes, etc. to wear out. 

If the thermostat is absent, you will be unable to warm up your engine, and starting a cold engine will cause damage to some engine components. 

Also, parts can wear out due to overheating because when coolant flows from the engine to the radiator, it does not stay there long enough to get cold before returning to the engine leading to overheating. The absence of a thermostat makes it impossible to control this flow.

Excessive fuel consumption

Driving without a thermostat will increase fuel consumption. 

An overheated or too cool engine temperature will increase emissions which will in turn increase fuel consumption. This is because the thermostat is faulty, and the engine is not able to reach its normal operating temperature, therefore, consuming more fuel than necessary in the process.

How to Inspect and Test a Bad Thermostat

When you start encountering problems with your thermostat, the best thing to do is to check it and possibly have it tested to know where the fault is coming from. 

Here are the procedures to get this done. 

  • Park your car in a good spot and leave the engine and radiator to cool down.
  • Open your bonnet and locate the thermostat. You can trace it by following the upper radiator hose to where it links with the engine. 
  • The thermostat housing is attached at the end of this hose. However, in some cars, it is attached to the lower and not the upper radiator hose.
  • Test the thermostat by removing the radiator cap to observe coolant flow.
  • Start your engine and leave it in the “ON” position then check the radiator filler neck to observe if coolant is flowing.
  • Coolant should not be flowing at this time because your engine has not yet reached the operating temperature which will require the thermostat to open. However, if the coolant is flowing already, it means the thermostat is stuck open and should be replaced.
  • If the coolant is not flowing into the engine after it has reached the normal operating temperature and the engine’s temperature gets high, it means the thermostat is stuck closed and should be fixed or replaced.
  • You can check the thermostat by using your palm to feel the temperature of the upper radiator hose to see if it is cold or warm. 
  • Auto shop operators test the thermostat using an infrared thermometer to check the temperature of the upper and lower radiator hoses and it is monitored with a scan tool.

Cost of Replacing a Car Thermostat

Make sure you buy a thermostat that is designed for your vehicle and has the same temperature rating as the original. A new thermostat will cost between $60 to $150 and with labor, the cost can be up to $150 to $400. This price also varies depending on the model and make of your vehicle. 

Replacing a thermostat requires few tools and is often regarded as a DIY-friendly repair job. This implies that you can easily have this done by yourself.

How to Troubleshoot a Car’s Thermostat

  • In troubleshooting your thermostat, the first thing to do is to check the coolant. Ensure it is in the right quantity and not contaminated. Mixing different types of coolants will cause debris to build in the thermostat or too much water will cause rusts which can cause the thermostat to be stuck open or closed.
  • Check your temperature gauge. If your engine’s temperature gets high within 15 minutes of driving your car and the temperature needle gets to the red area, it indicates that your engine is overheating, and your thermostat is probably stuck closed.
  • If the engine is hot but the upper and lower radiator hoses are cool when you’ve turned on your car for a while, then there is a problem with the thermostat because both hoses are supposed to be warm at this point.
  • If the thermostat exhibits any of the symptoms listed above, then there could be a leak as well in the thermostat housing due to excessive pressure on the thermostat.
  • To verify this, you will need a needlenose plier and water. Take the thermostat from its housing and place it on a pot of boiling water with the plier. You must heat the water to the exact temperature indicated on the thermostat. It could be between 180 to 212 degrees Fahrenheit depending on the type of thermostat.
  • When the boiling water gets to this temperature, the thermostat should open up. If it does not, it indicates the thermostat has failed.
  • The next thing to do is to test and replace the coolant because a properly maintained cooling system will increase the longevity of the thermostat. Endeavor to change the coolant according to the car manufacturer’s recommended change interval.
  • After testing and replacing the coolant, take the final step to replace the thermostat. You can easily do this on your own or at an auto repair shop.

Frequently Asked Questions about Car Thermostat

Why does my car Thermostat keep going bad?

There are several reasons your thermostat will go bad often. The primary reason is an overheated engine. Other causes can be contaminants like sludge in the thermostat, age, improper installation, and some minor defects.

If my engine takes too long to warm up, can it be because of a bad Thermostat?

A bad thermostat can delay your engine from warming up. This is because when the thermostat is stuck open, coolant flows uncontrollably from the radiator to the engine even when it is not needed. This will make the engine’s temperature drop below normal and run cold. Your engine will take too long to warm up or might not even get to the normal operating temperature in this case.

When should I replace my Thermostat?

Some thermostats can last for up to 10 years before they begin to wear out due to age. Other factors like poor maintenance, contaminants, and driving habits can cause your thermostat to wear out earlier than usual. When the thermostat goes bad, it will show some signs and will affect the normal operation of other engine components. When you notice all of these, it is important to replace the damaged thermostat to avoid further complications.

How do I know if I have a bad Thermostat?

If your thermostat is faulty it will begin to show some symptoms as discussed earlier. Some of those symptoms are an overheating engine, leaking coolant, high-temperature reading, and failure of the HVAC system to turn on.

Can I drive with a broken Thermostat or without a thermostat?

No! Driving with a broken thermostat is not safe. Doing this might cause your engine to overheat leading to damage to other components of the engine. Driving without a thermostat is also dangerous, especially in very cold regions. When you remove the thermostat, the engine remains cold since the coolant is just flowing freely from the radiator to the engine without any regulation. At this point, your car temperature reduces to 50°C which is very cold and will cause some components to wear out.

How do I know the kind of Thermostat my car needs?

Every car is specially designed, and its engine is programmed to work within a certain operating temperature to ensure optimal performance. To know the kind of thermostat your car needs, take note of the manufacturer’s recommendation for the model and make of your vehicle. From here, you will know the one that is suitable for your engine.