Why Is My Engine Running Cold?

What will happen when your engine runs below the optimum temperature? Does it cause damage to your engine car? Let’s find out the answer to the question “Why is my engine running cold?” in the article. 

Why is my engine running cold?

The optimum temperature for a car’s engine to operate effectively is in the range of 185-200F. 

At this temperature, the engine will work with the best performance and save fuel. If the engine is too cold, it will be difficult for the fuel to evaporate, resulting in poor performance and increased fuel consumption. 

Car engines running cold will be very harmful when used long-term. In addition, you will notice the amount of carbon buildup in different parts of the engine when your engine is always running cold. 

Therefore, the owner should learn about the cause and what are the symptoms of this phenomenon. So, what are the reasons:

Car thermostat not working

Your car’s thermostat regulates the flow of coolant through the engine, as they continuously check the temperature of the coolant and precisely regulate the coolant flow through the radiator to obtain and maintain the temperature, optimum engine performance.

There are two cases that lead to thermostat failure:

  • The thermostat is stuck in the opening position
  • Your thermostat got stuck in the closed position.
car thermostat not working
Check the car thermostat (Photo: istockphoto.com)

Signs of faulty thermostat:

A faulty thermostat is one of the popular problems in your car. You can completely DIY. We will list some symptoms you can easily realize when the thermostat falls:

  • The temperature gauge records high and the motor overheats.

The thermostat opens and closes to allow the amount of coolant into the engine. Inactive thermostats stuck in the closed position will cause the engine to overheat as coolant flow will be interrupted.

  • Leaking car coolant 

If you see coolant leaking on or around the mounting surface in your car, this is the sign of a faulty thermostat.

  • Temperature changes unusually

If you check that the display of the temperature gauge goes from hot to cold or vice versa. The reason is the thermostat not working properly.

  • Strange Engine Noises

A thermostat that doesn’t work can also make a  noise when your car’s engine starts to overheat.

>> See more: Drive A Car Without a Thermostat: All You Need to Know

Faulty coolant temperature sensor.

Faulty coolant temperature sensor
ECT will help the engine work effectively (Photo: flickr.com)

The coolant temperature sensor is also known as ECT is one of the very important sensors to help protect the engine, improve the working efficiency of the engine as well as help the engine stable operation. 

ECT prevents the engine from overheating and measures the temperature of the coolant to make sure it is balanced. The faulty coolant temperature is the most common reason that causes the car temperature gauge to stay cold.

Signs of bad coolant temperature sensor:

The coolant temperature sensor is mounted in the engine body and is in direct contact with the coolant. Knowing the symptoms will help you avoid the potential risks and take timely precautionary measures:

  • “Check Engine” light is on.

This is the most popular sign when the Coolant Temperature Sensor is falling. If you see the “check engine” light suddenly turn on, you absolutely should check the coolant temperature. And, the light does not turn off until you’ve fixed this error.

  • High fuel consumption

When the sensor is damaged or faulty, the sensor signal sent to the ECU will be erroneous and cause the ECU to incorrectly report the temperature of the engine.

So if ECT reports a cool temperature when your engine is really warm or hot, this will cause the car to use more fuel than necessary, thereby reducing fuel economy. And this will eventually prevent the performance of the engine. 

  • The engine is overheated

When the signal from this sensor is wrong, it will make the operation of the cooling fan incorrect. So sometimes the engine will overheat because the liquid is not cooled timely.

  • Reduced engine power

The engine needs an optimal mixture of air and fuel to achieve the highest power. There are many factors on the engine that affect the amount of fuel, but the main determining factor is the signal from the coolant temperature sensor.

>> See more: Is Coolant The Same As Antifreeze?

Clutch for the fan locked.

Clutch for the fan locked
A clutch fan is one of the most important reasons causes engine to run cold (Photo: flickr.com)

Do you know what the effect of clutch fans is? It is a type of thermal induction spring that works based on a liquid silicone solvent based on the temperature of the car coolant to work.

From the outside, it can be difficult to diagnose a locked fan clutch just by visual inspection. This is because the clutch will seem to work perfectly, as the fault is internal. Fortunately, there are several symptoms you can easily realize:

  • Overheating engine

Because the cooling fan does not provide the necessary amount of air through the radiator to cool the water. It will cause a higher temperature in the engine than normal.

  • Noisy sound

Excessive fan noise at high speed is caused by the same problem, the fan clutch is retained. This can cause bearing damage, damage to the radiator if the impeller bends too far, or even break the plastic fan.

  • Not enough heat

If the fan clutch is stuck, it remains operated continuously, the engine is cooling off too much. It will cause insufficient heat.

>> Related post: How a Fan Clutch Works in a Car


The article has given three reasons to explain “why is my engine running cold” and some basic signs to help you early detection of damage. In the next article, we will help you with how to fix it when the car running cold. Follow us to read another useful article!