Air in a Gas Tank: What REALLY Happens?! (Explained)

If you own or you’re familiar with modern models of vehicles, you’ll know that the gas tanks are sealed. Such a feature is to avoid air from getting in the tank. Thus, if your car is letting out air, it means some amount of it got inside. However, you may wonder what its effects are and how you should deal with it. So, you may ask:

If there is air in a gas tank, what really happens? If there’s air in a gas tank, it can mean that the vapors don’t get released back to the engine. The air can cause pressure to build up in the tank. If it starts producing air bubbles, it can lead to stalling and eventually disabling your car to start.

There’s a reason why modern vehicles have gas tanks sealed to prevent air from getting inside of them. If there’s air inside, the pressure can increase. Moreover, it may produce fuel bubbles which can lead to stalling. If the bubbles continue to form inside, the engine can start stalling and eventually stopping.

This article will walk you through the possible effects of having air in a gas tank. This way, you can understand the risks it entails. Moreover, you can know what to do and how to deal with such if it ever happens to you.

Without any further ado, let’s get into it!

Air in a Gas Tank

What Happens When Air Gets in Your Gas Tank?

If air gets in your gas tank, it can cause air bubbles in the fuel line. Such bubbles can cause inefficient combustion. 

As a result, it can cause your engine to start stalling as you drive. Moreover, it can begin experiencing hiccups.

If the bubbles continue to form and ruin your engine, it can also lead to disabling your car, not allowing it to start.

For this reason, you must always keep your fuel lines free of air. This way, you can enjoy a smooth drive in your car.

So, you may wonder if it’s a bad thing to have air always inside your gas tank.

Is It Bad to Get Air in Your Gas Tank?

Yes, it isn’t good to get air in your gas tank. However, the effects it causes, such as stalling, hiccups, and refusal to start, mean there’s something wrong with your engine.

As mentioned earlier, the air inside the gas tank causes pressure to build up. Now, while a pressure build-up is normal for every gas tank, it’s not a great thing.

For this reason, most engines have a vapor recovery system. Thus, when you make some errors, such as overfilling your tank, it can lead to spillage or leakage.

Such things cause the vapor to pollute the air, which can all be harmful if you breathe some of it. Another thing to note is that the repairs of such can be pretty expensive, which means it would also harm your wallet.

What Causes Air in the Gas Tank?

Most air in a gas tank occurs when the evaporated gasoline remains in the air, the fuel still stored in your gas tank. 

Now, since vapors make more pressure than the fuel, the pressure continues to build as the tank continues to lessen the fuel it contains.

Another thing that can happen is that your gas tank has some leakage or some holes that let in air. If such a thing is the case, you’ll need to have your engine fixed soon. Otherwise, it may cause more trouble and issues in the long run.

Now, the question is how you would get the air out of your gas tank. If it ever happens to you, how should you deal with it?

How Do You Get the Air Out of Your Gas Tank?

To get the air out of your gas tank, you need to purge the air from the side of the fuel system that has low pressure.

Afterward, you must open the fuel lines and allow them to bleed ports downstream of your fuel pump. It would be best if you started with the one closest to the pump, working your way outwards. It would be best if you continued doing so until the fuel runs out.

Now, if you suspect a hole or leakage in your tank, get your engine checked by an expert soon.

This way, you can make sure that your engine remains safe and that no further issues would occur due to such a problem. Here’s how you can know if your gas tank has air inside of it.

air in gas tank

Air in a Gas Tank Symptoms

If you think your gas tank has air in it or has air in the fuel line, you can know it if you experience the following symptoms.

  • Stalling
  • Hiccuping
  • Refusal to start

If your engine encounters any of the following issues, it would be best to have it checked by an expert immediately. In this manner, you can ensure that your engine is safe and that no more problems arise due to the problem.

To keep your automobile operating smoothly, keep your fuel lines clear of air. Moreover, maintaining such can give you a smooth and well-performing engine for a long time.

Air Sound When Opening the Gas Cap – Is That Ok?

If you hear some hissing sounds when you open the gas cap, it may be due to the air inside the gas tank.

In general, it’s alright to hear such sounds once in a while as the pressure and air increase.

However, if you hear it frequently and your engine stalls and stops most of the time, it would be best to have it checked.

Suppose you hear or experience the air sound when opening the cap. In that case, it’s usually because the gas tank vapors don’t get routed back to the engine.

Thus, it would be best if you had it checked for an immediate solution and repair. If left unchecked, it could lead to further issues with your engine. Moreover, it can harm your engine’s overall performance in the long run.


In a nutshell, air in a gas tank is not a great thing for the engine and the fuel system. When there is air in a gas tank, the vapors may not be released back to the engine. The air might cause a pressure build-up in the tank. If it starts creating air bubbles, it might cause stalling and eventually destroy your car’s ability to start.

There’s a reason why newer cars’ gas tanks are insulated to prevent air from getting inside. If there is air within, the pressure may rise. It may also produce fuel bubbles, which might lead to stoppage. If the bubbles inside the engine continue to grow, the engine will eventually slow and stop.

As a general rule of thumb, if you detect a hole or a leak in your tank, you should seek an expert’s assistance. As soon as possible, have your engine inspected by a professional.

This way, you can ensure that your engine is safe and that no more problems arise due to the problem.



Image credits – Canva

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My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more