Buzzing Sound Under Car When Off? Common Causes You Never Knew!

Do you hear a buzzing sound under car when off?

Perhaps you just turned off the engine after taking your car for a spin. But suddenly, you hear a buzzing sound underneath. What gives?

There are several reasons why this happens – and the problem can vary from mild to severe. Let’s explore these reasons and get to the root of this issue once and for all!

buzzing sound under car when off

Causes Of Buzzing Sound Under Car When Off

After a busy day, nothing feels so much better than having to turn you engine off and head into the house to relax. But if you hear a buzzing noise from the engine even when it is off, this may start to worry you. After all, your engine is supposed to be quiet once off, right?

Then, you may start to wonder if you need to get your vehicle repaired. Or if it will be an expensive fix. Surely, nobody would want to spend a fortune on car repairs!

But before you panic, keep in mind that there are a few reasons why this happens. Some of the causes are simple and not at all an expensive fix. Yet, others could mean more serious trouble. For instance, it could be due to a coolant leak, or perhaps there is air stuck on the heater core. 

Now, let us look into these common causes of buzzing sound under car when off:

1. Engine shutting down

It could mean nothing but the engine is still shutting down. Inside the engine, there is an electric motor equipped with cooling fans. Once you have turned your engine off, this also stops the electric motor from producing electricity. Then, the cooling fans slow down until they stop completely. 

You can even check the fans and the motor winding down slowly. The best way to do this is when you pop your hood open after turning the engine off. In this case, there is absolutely nothing to worry about as it is completely normal.

2. There is damage to the head gasket

Next reason is that your head gasket may be completely damaged. It may be malfunctioning, broken, or has several issues that simply appear out of nowhere. When you have a damaged head gasket, this can increase the likelihood of a coolant leak. Moreover, motor oil can mix with your coolant, which can be a big problem.

Water vapor will then enter the engine system, then it goes out of your tailpipe in the form of a white smoke. This is why if your head gasket is defective, you need to get it fixed sooner than later.

3. Air is trapped in the heater core.

Your heater core is not supposed to have air around or in it. Once this happens, though, it will cause an air bubble to be lodged in your heater core. Then, various problems can arise such as damage to the head gasket and hose pipe leaks.

4. Insufficient coolant

Your vehicle relies on coolant to keep the engine in good condition and prevent overheating. However, if there is insufficient coolant, this will cause some problems to your engine. Moreover, having air trapped in your coolant system can trigger a buzzing sound from your engine upon turning it off.

It is also possible that there is a leak in your coolant chamber or hose. Once the leak exposes your coolant to the engine’s hotter parts, you can tell right away because of a sweet smell originating from the engine after the ignition has been turned on.

If you think there is a coolant leak issue in your vehicle, be sure to have this addressed immediately by a mechanic. You need to have this problem resolved since having a coolant leak means having inadequate supply of coolant to your engine – and this can increase the risk of overheating.

5. A normal occurrence from the fuel evaporation leakage checking system

First of all, the EVAP is responsible for detecting even the slightest leak in your fuel filler cap, as well as the EVAP canister valve. There is a buzzing noise due to the small vacuum it creates that checks for any leaks. 

Additionally, the EVAP removes hazardous vapors around your engine system. It prevents these vapors from escaping into the atmosphere. This is why in a place that has a smog issue, it could be possible that the EVAP system is not working as it should.

How To Address The Buzzing Sound Issue

With all these things in mind, it is important to know the actual cause of the problem, so you can go ahead with the steps to fix it.

If the buzzing noise is due to a gasket damage, then you need to have this replaced or repaired by a mechanic. 

But if the issue is with your EVAP, such as any malfunctioning problem to the system, you need to have it fixed. During a tune-up session, have the mechanic check this system to make sure it is doing its job properly. 

When there is a coolant leak, it may be necessary to have the radiator hoses, hose clamps, or even the radiator replaced to resolve this leak issue.

And lastly, in the case of a faulty head gasket, the only way to deal with it is to have it replaced. Typically, it should cost about $1000 to as much as $2000 including labor fees.

Read More: Understanding the Uconnect Box Requires Service Message

Wrap Up

Hearing a buzzing sound under car when off can be quite concerning. You may worry about the safety of your vehicle or if there are big issues happening that can negatively impact your engine’s performance and lifespan.

This is why when you hear this sound, make it a priority to determine the actual cause of the problem. We have shared the possible reasons for this noise, as well as the ways to address these causes. Then, you can have the peace of mind each time you use your vehicle and not have to deal with this odd buzzing noise anymore.

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