car overheating when idle
Vehicle maintenance

Why Is My Car Overheating When Idle?

Cars can overheat at any time. It usually happens when you are using your car on a long journey and/or driving in really hot weather. However, there are some exceptions to this as well. Speaking of exceptions, you might be wondering why your car is overheating when idle.

Normally, a car engine can overheat due to not receiving sufficient coolants, but this is not the only reason why this happens. If you want to find out all the possible reasons why your car is overheating when idle, you’ve come to the right place. With that said, let’s get started. 

Reasons Why Your Car Is Overheating When Idle

If you are reading this guide, chances are that you are facing this common issue. You might have checked everything and found nothing that would explain why your vehicle is having this problem. Don’t worry, because we’ll explain all the major reasons why this issue can happen and how you can avoid it. 

We’ve listed some of the most common reasons down below. Let’s dive right in and take a look at what causes this problem and how you can fix it. 

Low Coolant Level

Like we said, one of the main reasons why an engine overheats is a problem with the cooling fluid. Using high-quality cooling fluid is essential because it disposes of excess heat from the engine. Keep in mind that this issue can also happen if the cooling fluid is about to run out. 

A good way to prevent this problem is to always make sure that the engine has an optimal coolant level. Plus, you should also keep the outside temperature in mind. Use a high-quality coolant with a proper boiling point.

On top of that, if the coolant is contaminated, you’ll face the same results. If you’ve checked the quantity and there is ample cooling fluid in the engine, then it means you need to replace it since it has been contaminated.

car overheating when idle

Clogged Radiator 

Just like an air conditioner in your home, cars also have radiators that have small passageways where oil passes. However, water can expand due to excess heat, meaning that the cooling fluids are not moving at the speed that they are supposed to. In some rare cases, the radiator passageways can even get clogged.

This would naturally mean that the fluids are not as effective as they normally would be. In turn, it would cause your engine to overheat and the engine light to turn on.

To fix this, you can get your car’s radiator serviced. Usually, a good mechanic will service your radiator for about $100 to $150. However, that’s only if your vehicle requires a small service. If you need to get your radiator replaced, you’re looking at an expense of about $1300.

You can always use the proper amount of water in your radiator at all times to protect it from damage. We know that it can feel like a chore, but it will help you out in the long run. Plus, a clogged radiator can occasionally cause your car to jerk

Broken Radiator Fan 

Having a broken or faulty radiator fan is extremely dangerous as it will completely stop the airflow of your vehicle. When your car is moving, the airflow moves the heat from the coolant to the radiator. However, when you are stationary, the fan cools your engine down, preventing it from overheating.

Usually, cars either have an electric radiator fan or a belt-driven one. In the case of an electric fan, the switch or relay might be faulty. With a belt-driven fan, the belt might be loose, causing it to not work properly. If your car is overheating when stationary, we suggest that you check the radiator fan and get it replaced if it’s broken.

To know for sure if the fan motor is broken or not, you should keep an eye on the temperature of the car. If it goes to red when idle and goes down when moving, it probably means that the fan is not working as intended and a bad radiator is the main cause of this.

car overheating when idle

Faulty or Bad Thermostat Valve

In case you’re not aware, a thermostat valve turns on the radiator fan when your vehicle is idle. If your fan isn’t working, it might not necessarily mean that the fan is broken. It might mean that the thermostat valve is faulty. This could be due to a damaged or broken valve.

Unfortunately, if this is the case, then you have no choice but to replace the valve. This costs about $150 to $200 depending on the model of your vehicle.

However, you won’t notice this issue immediately. It’ll only come up when the engine reaches operating temperatures. At that point, the gauge will move towards red, indicating that there is a problem. 

The Water Pump Might Be Malfunctioning

The water pump has the task of pumping cooling fluids through the system. Normally, these pumps are belt-driven, so if the belt is damaged, the water pump will cease to work properly. However, sometimes, the pump itself gets damaged and the only way to fix it is to replace it. 

If that is the case, do not attempt to take on the challenge yourself. Instead, we highly recommend that you contact a certified mechanic and let them take a look. Usually, water pumps are not expensive.

Can Overheating Cause Damage?

Now that we’ve discussed some of the main reasons why this issue occurs and how you can stop it from happening, let’s take a look at how overheating can cause damage to your engine. 

If your engine continues to run after being overheated, the coolant inside will start to boil up and emit steam. This will not only cause a bad smell, but it will also cause irreversible damage to your engine and other components of the vehicle.

Examples of major damage include bent rods and frozen cooling systems. These are just some of the many bad outcomes. That is why it is crucial that you maintain a good temperature in your engine and get your car checked immediately if it starts overheating. 

Mixing Water With Antifreeze

While antifreeze is good at lowering the temperature, it is not great at transferring heat from one place to another. That is why it is essential that you mix it with water. The consistency will allow the antifreeze mixture to transfer heat without any issues while keeping the temperature stable. 

Oftentimes, some mechanics straight up put antifreeze in your engine due to a lack of awareness. This is one of the big reasons why your engine is overheating. If this happens to you, we suggest that you drain out some of the antifreeze and add a bit of water to it. Fortunately, antifreeze isn’t expensive.

car overheating when idle

How To Stop Your Car From Overheating

There are various ways in which you can stop your car from overheating. Following these steps will allow you to protect your car and enhance its longevity. First of all, we suggest that you try to park your car in the shade whenever possible. Parking it in direct sunlight will eventually cause damage to your engine.

On top of that, parking in the shade is also good for the windows of your car, and it allows your vehicle to be cooler when you get in after a long day of work. Additionally, you can leave your windows slightly open to let air pass through. This can also be done when you are stuck in traffic and do not want to turn on the A/C.

You should get the temperature gauge checked out to see if it is faulty or not. Sometimes, you might have a bad temp sensor, and it will show that your car is overheating when it isn’t. Before panicking, we suggest that you take your car to a certified mechanic and get it checked out. 


That’s all there is to understand about why your car is overheating when idle. The main reasons for this are a faulty thermostat, broken radiator fan, clogged radiator, and low cooling fluids. If you cannot find any issue, we suggest that you get your car checked by someone who is knowledgeable about vehicles. This will allow you to pinpoint the exact issue and fix it. 

Plus, a certified mechanic can also check to see if the gauge is faulty or not. Chances are that the gauge is displaying the wrong information due to a malfunction. In any case, make sure that you go to a good mechanic and get your car thoroughly checked.