Loud Fan Noise When Car Is Turned Off - Any Problem or Normal?

If you're just getting to your destination after a long ride, you might notice a loud fan noise coming from your car engine house. The noise may be regular, but you just haven't noticed it till now. However, it could be irregular or louder than usual while running for longer than it should.

The loud noise can cause you to worry and leave you wondering what caused the issue before now.

If you notice a loud fan noise after turning off your car engine, it is usually a normal operation in your engine compartment, the fan is just cooling the engine according to the program and doesn't care if you turned off the ignition or not.

This operation is meant to transfer air through the engine or cool down the engine house. However, if the fan is still running loudly for longer than 5 to 10 minutes, then there might be issues that need professional attention.

Here is what we will cover in this article:

• How Car Cooling System Works?
• Why Cooling Fan Makes Loud Noises When Car is Turned Off?
• How To Troubleshoot Loud Fan Noise?

How Does a Car Fan Cooling System Work?

All vehicles have internal engines, which facilitate the smooth running of the car. However, to run properly, the combustion engine must have enough heat to prevent premature wear. Moreover, too much heat in the internal engines can condemn the engine or cause extensive damage to its surrounding components.

This is where the function of the cooling fan comes in. The cooling fan ensures the engine and its components are at an optimal temperature level. 

In short, the vehicle's cooling system functions by transferring the engine heat to the antifreeze, which moves to the radiator and releases the heat to the air outside. The process starts again as the antifreeze returns to the engine. 

Though the process sounds simple, it also depends on various cooling parts to keep the engine temperature at a balanced level.

Now that you have a general idea of how the car cooling system works, I will explain the cooling concept while your engine is running and when it is turned off. 

When you are on the road with your vehicle, your engine is running - it will be quite odd if it doesn't, though - which means the air is transferred to the radiator. This helps the engine to cool down when it's too hot and eventually keep the working temperature. 

However, when you turn off the ignition, the coolant or antifreeze does not circulate, and the heat will remain trapped in the engine compartment. This means the engine will be hotter than usual, making cooling time longer. But the cooling fan will keep functioning until the engine is cool enough. Well, this is how it worked in some cars. I believe, new vehicles just stop the fan whenever you turn off the engine.

Why Does Your Cooling Fan Make Loud Noises When Car Is Turned Off?

If the cooling fan in your vehicle continues making loud noises after you turn off the car engine, it is due to the amount of heat accumulating in your car system. When your car cooling fan system continues running while your engine is turned on, it generates a noise - which is a normal occurrence. But it becomes louder as the engine sound is turned off when you turn off the car ignition.

However, if the noise persists for too long or is louder than usual, then there might be an issue(s) with the fan cooling system. Some of these issues include:

• Faulty fan relay
• Debris on the fan blades
• Failing fan motor
• Low coolant level
• Cracked radiator, among others

As vehicle owners, we expect our cars to run as smoothly and quietly as possible, especially when it is not moving. However, you might notice the noise your cooling fan makes while it's functioning after you turn off your engine. 

As I stated before, your engine fan should not run for more than 5 to 10 minutes after turning it off. If it does, then there is an issue with the cooling system. Here are more details on the reasons behind this issue:

1) Low Coolant Level

The coolant level of your vehicle is the first thing you should check to find out why your car engine fan is running for too long. If the level of the coolant is low, it will increase the cooling time of the engine, thereby increasing the fan running time.

Your vehicle's coolant level is low if it is below the minimum line. You can inspect this by opening your coolant reservoir. If the level is low, you can add more coolant to the reservoir. 

2) Cracked Radiator

Another reason your fan is running for long after you turn off the engine is due to a faulty or cracked radiator. The radiator circulates the coolant through the engine house. 

If it cracks, it leaks the coolant into the environment, which increases the level of work the fan would have to perform after you turn off the engine. A leaky radiator could be due to incidents such as an accident or poor maintenance.

3) Faulty Fan Relay

The fan relay is responsible for powering the engine cooling fan. If the cooling fan relay develops faults, it will cause the engine fan to function for longer than it should to cool the engine down. Some reasons for a faulty cooling fan relay include the following:

• Corrosion
• Wear and tear
• Overheating

If you are sure this is the cause of the problem, take your car to a service center for testing, repairs, and replacement, if necessary.

4) Leaking Thermostatic Housing

The thermostatic housing regulates the flow of coolant to the engine. Therefore, a leaking thermostatic housing can cause the fan to function for longer. Once the housing starts leaking, the coolant level drops

This means that there won't be enough coolant to cool the engine, thereby increasing the running time of the cooling fan.

5) Faulty Cooling Fan

Last but not least is the faulty cooling fan issue. The engine cooling fan cools the heat in the combustion engine by blowing air consistently on the engine compartment. If the fan has developed faults, it is often due to issues such as:

• A broken blade
• Blockage in the airflow
• An electrical issue

A faulty fan cannot cool the engine properly as it might be slower while making unusual noise and thus causing it to run for longer than necessary. 

How to Troubleshoot Loud Fan Noise

Though the reasons why your fan makes loud fan noises may vary, you will have to confirm the cause before making decisions about how you can troubleshoot it. Below are some possible solutions to the cooling fan issue:

1) Disconnecting Your Batteries

The first and also simplest step to correct this problem is to disconnect your battery. Once your fan is still operating after ten minutes:

• Open the hood of your vehicle and locate the engine battery.
• Disconnect the negative side of the battery's cable.

 This process will help you keep the battery from getting drained from the running fan issue.

2) Adding Coolant

If the problem is that your coolant level is low, you can increase the level of coolant. If the coolant is low, it means the internal engines will be hotter, requiring the cooling fan to operate for longer than it should keep the engine cool. 

3) Inspect the Cooling System

If you can't seem to find the cause of the cooling fan issue, you might need to check your vehicle's cooling system. However, if it turns out that the cooling system is malfunctioning, it could cause the fan to run for longer intervals. While inspecting your cooling system, check for:

• Faulty hoses
• Visible leaks
• Radiator issues
• Correctly sealed radiator
• Faulty thermostat

These issues could be the reason your engine is heating up and the fan is running loudly for longer than usual.

4) Check the Fan's Switch

This is the power control of the engine cooling fan. Therefore, it might be the reason your cooling fan is acting up. If the switch is faulty, it can cause the cooling fan to stay on for longer than required. 

To fix this issue, locate the fuse box in the engine compartment and inspect the fan switch for signs of heating or faults. However, replace the fan switch with a similar but better switch if it is faulty.

5) Take Your Vehicle to a Professional

If you are skeptical about checking and fixing the cooling fan issue yourself, you can take your car to a qualified automotive technician. The auto mechanic can perform a detailed inspection, run necessary tests and guide you on how to resolve the issue.

Final Words

Your fan might be functioning normally once you notice its noise. However, it could be an issue if it runs for longer than normal.

Now that you have an idea about how your vehicle's cooling fan works and also possible reasons why it keeps running with a loud noise, you can easily find a solution to the issue. However, if it is an issue that might require expert opinion and evaluation, you might have to take your vehicle to a qualified mechanic.