8 Reasons for Fan Noise When Your Engine Is Off

car fan noise

Last updated: June 29, 2023 at 12:11 pm

We’re all used to our cars making noise, but usually, the noise only occurs when the car is in use, when the engine is turned on.

If you’ve noticed that your car is making noises when your engine is turned off, you may be concerned. But do you need to be?

What Causes Fan Noise After My Engine Turns Off?

1. Cooling Fans

In many vehicles, the engine’s cooling fans will stay on for two to three minutes after the engine has been turned off. This allows them to successfully cool the engine down. In some cars, this might even be as long as around five minutes.

If you notice that your fans are on for anywhere up to five minutes after you turn your engine off – do not panic. It is likely that they’re designed to stay on a little longer to keep the engine from overheating. The issue comes, however, if your fans seem to still be on after five minutes.

Also read: 7 Main Causes of Whistling Noise From a Car

2. Low Coolant Level

Fans running longer than five minutes can be caused by several things, one of which is low coolant level. Coolant prevents your engine from overheating when it’s warm outside, and it helps to protect your engine from freezing when it’s too cold. It also lubricates certain moving parts.

If there is not enough coolant present, it will inevitably take the engine much longer to cool down. This then means that the fans must work harder to protect the engine and get it below the desired temperature.

If your coolant level is below the minimum line when you open the coolant reservoir, then it is likely the culprit. To fix this issue, simply add more coolant to the reservoir.

engine coolant

3. Leaking Coolant

Similarly, an issue with the radiator or reservoir (or several other things) may lead to coolant leaks. This then reduces how much coolant is available to cool the engine, and as a result, you end up with the fans working overtime.

If you believe there is a chance that your engine is leaking coolant, it is important to check it out. You can do this yourself if you are knowledgeable enough, or alternatively take your vehicle to a professional.

4. Faulty Electrical Wires

The wires that connect the engine fan to the battery may also cause the fan to run too long.

If they are damaged or faulty, the messages sent along them might get mixed, leading to the fan being left on longer than necessary.

5. Leaking Heater Exchanger

heater exchanger

The heater exchanger basically heats the car. When it leaks, it causes the coolant levels within the vehicle to drop.

As a result, there is less coolant to keep the engine cool and so the fans must pick up the slack.

6. Engine Overheating

There are a number of things that might lead to your engine overheating. It is always something that you should get a professional to look at, though. It is also something that can cause your fans to continue running after the engine is off.

Since the fans’ job is to keep the engine cool and stop it from overheating, they will run until the engine cools down, which when it is overheating, can take a lot longer.

7. Faulty Cooling Fan

Just as with coolant, the cooling fans are essential in preventing the engine from overheating. They protect the engine by blowing air over it. Sometimes, though, when they break, they are no longer able to do their job as effectively as before. This leads to the engine fans running for much longer.

A cooling fan may suffer from a broken blade, an electrical issue, or a blockage, all of which should be checked and repaired as soon as possible to keep the engine cool.

8. Leaking Thermostatic Housing

The thermostatic housing is responsible for transporting and regulating the flow of the coolant to the engine. When this breaks, insufficient coolant reaches the engine.

As a result, the engine may begin to overheat, and in return, the cooling fans must work overtime to protect the vehicle.

Related: Fan Belt Noise: How to Fix a Squeaking Fan Belt

What Can You Do About Fan Noise?

Those with little mechanical skill or knowledge should always take a vehicle to a professional if they are concerned that something untoward is going on.

If you have some skill, you may want to try one of these solutions to a fan noise after the engine is off:

Add Coolant

As mentioned above, one of the first things to check – and one of the easiest things to fix – is the coolant level of your vehicle.

If the coolant level is low, then it is likely that is what is causing your fans to continue. Simply add in some more coolant and see what happens.

Disconnect Batteries

If your fans simply are not turning off, and you’re concerned about the vehicle and the battery life, you can just disconnect the battery.

This will help to save the battery and will turn your fans off.

Better Safe Than Sorry

If your car is making a fan noise after the engine has been turned off, and it has not done it before or the noise is continuing for longer than five minutes, then it is important that you get it checked.

You should be aware that issues in vehicles can be dangerous if left unattended, so it is crucial that you or a mechanic look at the car as soon as possible – this will prevent any further damage occurring and could also help to protect you!

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About the Author: AJ

AJ is a self-confessed soundproofing nut. He has written full-time on Quiet Living for the past 4 years, and has a wealth of knowledge about living a quieter life, soundproofing and fixing loud noises.

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