Table of Contents

Introduction

The engine is the main component of any vehicle, and a malfunctioning engine means that your car will not be able to travel a long distance. For all the valid reasons, experts advise taking extreme care of the engine.

If the desired cooling phenomenon does not occur at the right time, the temperature can become so high that it can damage different engine components. An engine temperature warning is thus designed to alert the driver that something is wrong with the cooling phenomenon or that the engine requires some rest before moving on. This warning light signals that the drivers should take necessary steps to cool off their engine to avoid any particular damage.

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The warning sign can appear as a thermometer or ‘TEMP’ depending upon the vehicle model.
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But in any case, the drivers must pay attention to this warning sign considering it a sensor error as it can even cause an engine to seize.
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How does the Engine Cooling work?

An engine is a combination of fixed cylinders and moving pistons. Depending on the engine’s power, these cylinders and moving pistons can vary in car models. The primary function of an engine is to combust the fuel that pushes the piston, which in turn rotates the crankshaft (4). Finally, the vehicle moves through a system of gears in the powertrain. Thus, the combustion of gases and the movement of different parts in an engine create friction that increases the heat of the entire system. A typical engine has around 2000 moving parts that can depict the friction produced in an engine. Although engine oil lubricates different parts, decreasing the friction, the combustion of gases increases the overall temperature of the system. According to the experts, an optimum engine temperature is between 75 and 105 degrees Celcius (1). In cars, there is a cooling system specially designed to absorb the heat of an engine. This cooling system drives a coolant using a water pump that passes through the cylinder block (2). The coolant passes through different channels across the engine and absorbs the engine heat.

This coolant enters the radiator after leaving the engine, cooled by the air flow entering through the grill. Hence, the cooling system depends on the coolant inside the reservoir and the radiator fan that cools down the coolant and prepares it for further flow.
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Reasons why Engine Temperature Light Turns on?

The engine temperature light is present on the right side of the gauge, and this temperature gauge helps in monitoring the temperature of the engine system. The engine’s temperature remains below 100 degrees Celcius under normal conditions, and a warning light does not appear. If the engine’s temperature exceeds 100 degrees, the warning light appears, indicating an error in the engine system (1). The engine temperature measuring gauge is different from the oil temperature measuring gauge. There are other parts in the engine that helps in measuring the performance of the engine (2).

There is a thermometer that measures the temperature and determines the coolant level. The information is sent to the computer when the problem is specified, and the warning light is indicated to avoid any incident.
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Less Amount of Coolant

The warning light may appear due to the low levels of the coolant. The coolant usually drops below the level when there is any leakage in the hose. Coolant plays an important role in the vehicle’s engine as it prevents corrosion in the engine (3). Moreover, the coolant in the engine helps the engine from damage and helps maintain the pressure.

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When the coolant level falls below the level, the engine requires more pressure, and as a result, the engine is overheated. If the coolant drops the safety line, the engine warning light indicates that water and coolant levels are below the level and the engine system requires maintenance.

It is thus recommended to check the coolant before leaving on a long journey. Further, a driver should also check the coolant weekly if the car travels daily. This will ensure that amount of coolant in the reservoir is sufficient and the engine does not overheat. If an engine becomes hot, a driver should wait to open the cooler reservoir at a time. It is because the coolant can become boiling and come directly out of the reservoir, causing burning. So, check the coolant level and fill the reservoir to avoid engine heating. If the coolant level is falling rapidly, there might be an issue with the radiator components, or there can be a leak in the reservoir. In this case, take the car to a professional mechanic for further inspection.
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Defected Thermostat

There is an important part of the cooling system known as the thermostat system in the engine, and the main aim of this part is to measure the engine’s temperature. When the car’s engine operates at average temperature, the thermostat detects the engine’s functioning and restricts the coolant from flowing through the engine (1). On the other hand, when the engine’s temperature is above average, the thermostat detects and immediately allows the coolant to flow through the engine and radiator. The radiator plays a vital part in removing the excess heat from the engine into the atmosphere and helps normalize the engine’s temperature.

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There are chances that the thermostat might stop operating, and as a result, the temperature detected by the thermostat is not accurate. As a result, wrong information regarding the temperature will be sent to the onboard computer, and a warning light indicates that the engine’s temperature is high and requires sudden service.

Otherwise, severe damage might occur as the thermostat sensors are not operating (2). Due to this issue, the coolant will not be able to flow between the engine and radiator, and the system’s temperature will keep increasing.

A thermostat plays a critical role in the coolant flow across the engine. And a faulty thermostat can seize the engine if ignored for a long. Thus, take your car to a professional mechanic to get the defective thermostat replaced before it causes some significant problems in your vehicle.

Mechanical Damage

Another primary reason for the illuminated warning light may be the internal mechanical damage in the engine. An engine has various parts, such as radiators, water pumps, and cylinders. If any of the features would not operate correctly, the engine performance might be impacted and overheated (2).

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If the cylinders or the engine blocks are damaged, then there are chances that the coolant will start to leak, and hence the overall temperature of the engine will be increased.

Other than it, there are chances that leak coolant will get mixed with the engine oil or the lubricant. Engine oil is essential as it helps lubricate all the parts in constant friction.

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When engine oil is mixed with the coolant, the engine’s moving parts will not be well lubricated, and as a result, friction between the features increases. Due to the constant rubbing of the mechanical parts, the engine’s temperature rises, and performance is reduced.

There are chances that due to excessive heat production, the internal engine parts will get expanded (4). This would generate further problems in the valves and pistons.

Other than it, there is a water pump inside the engine. The water pump has multiple blades, and it helps in circulating the coolant through the machine. However, in some situations, there are some defects in the water pump due to errors in the timing belt or the timing chain. In addition, due to the defective water pump, the coolant will not be forced toward the engine, so the engine will excessively heat up. To avoid all these issues, the engine temperature light is lightened to indicate the problems on time.

Engine parts are complex that a simple driver cannot comprehend. Even taking out an engine at home is a difficult task. Thus, take the car to a professional mechanic or service center to get the engine checked if the temperature warning light is frequently flashing. With the repair of a few parts, the driver will save the cost of replacing the whole engine in case of seizing.
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Faulty Cooling Fan

Other than it, a primary reason that can increase the engine’s temperature is a defective cooling fan. The engine’s radiator operates on the cooling fan to supply the air when the car is driven slowly (4).

If there is an issue with the fan, such as electrical connectivity or defected motor, the air will not be supplied, and the warning light will turn on to indicate the overheating of the engine.
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A faulty cooling fan will not decrease the coolant temperature. Hence it will not be able to absorb the heat from the engine. This issue should also be resolved soon to avoid damage due to high temperature.

Common Repair Expenses

Following table illustrates the common repair expenses:

Common IssuesCost Required to Resolve the Issue
Less Coolant$100-200 for standard coolant change
Defected Thermostat$190-240 to replace the thermostat
Mechanical Damage$300-1000 to replace radiator, $460-640 to replace water pump, $2000-3000 to replace cylinder, $900 to replace valve piston
Faulty Cooling Fan$300-500 to replace cooling fan
Labor Cost$20-150

Personal Experience

My personal experience with the engine temperature warning light has been very bad. I remember traveling on a family trip towards the eastern side when my Honda Accord started showing the engine temperature warning light. Although, I stopped the vehicle for a while to decrease the engine temperature. Yet it was not enough as the temperature warning light again started blinking after traveling a few kilometers. In addition, my radiator fan stopped working, so the coolant temperature was not decreasing. So, I had to tow my vehicle and rent a car to complete the family trip. But my experience and cautiousness saved the vehicle’s engine from further damage. If I continued the journey while ignoring the light, I would have to pay hefty charges to replace my engine.
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Conclusion/Key Takeaway Points

So, the engine temperature warning light indicates a high temperature or some component failure that plays a significant role in engine cooling. In any case, there is a chance that the engine temperature is either up or will move up, which can cause damage to the engine components. The primary reasons that cause an engine warning light include less coolant, defected thermostat, mechanical damage to the engine’s features, and a faulty cooling fan. The driver should only drive the vehicle when this light displays with the appropriate steps. Because a high-temperature engine can seize up, resolving the issue will take greater expense.

FAQs

When the engine temperature warning light is displayed on the vehicle’s dashboard, it is recommended not to drive the car. This is because a severe problem in the cooling system or the engine can cause the engine to seize when the vehicle is driven. However, you can drive the car in case the coolant is low by refilling the coolant reservoir.

The coolant is boiling, which can come immediately onto the skin, causing skin burns. So, you are requested to cool the reservoir cap with water. Then take a cloth and slowly open the reservoir cap before taking it off. Then slowly take the reservoir cap away while protecting your hand. It is also recommended to keep your face away from the reservoir.

You can check the basic wiring of the coolant fan. If the wiring is fine, then there can be a chance that the fan has blown and needs to be replaced. But sometimes, the coolant fan does not work due to some circuitry issue that must be replaced before driving long distances.

References

About Author

Andrew Ray

Andrew is an automotive technician with 10 years of experience mainly in American and Japanese cars, covering everything from routine vehicle maintenance and engine inspections to tire rotation.