Maintenance Tips, Tricks And Hacks For Your Vehicle

Can Air In Brake Lines Cause Pulsating? (Answered!)




If you’ve been driving for a while, you may have experienced something strange when braking. You press down on the brake pedal and feel a pulsing in the pedal or steering wheel.

Immediately you think, can air in the brake lines cause pulsating?

In this blog post, we will discuss what can cause brake lines to pulsate and how you can fix the problem.

Key Takeaway

  • Brake pulsation is when you hit the brakes and you feel that the brake pedal is pulsating, moving up and down.
  • Air in the brake lines can cause reduced braking power, increased stopping distance, or complete braking ability, but not brake pulsation.
  • Air in brake lines isn’t able to get out by itself.
  • Air can get inside the brake master cylinder and cause a spongy brake.

What Is Brake Pulsation?

Brake pulsation is something that generally happens after your brakes are warmed up from driving a bit and when you press the brake pedal, you feel that your vehicle is shaking a bit.

Let’s say that you have been on a nice long road trip and you step on the brakes and you happen to notice a little shake. You are trying to figure out what it is. It’s called a brake pulsation.

Brake pulsations usually occur when the brakes are warmed up from driving. It is more likely that you will feel brake pulsation on warmed brakes than on cold brakes. If you step on the brake as soon as you leave the driveway, you are probably not going to feel anything.

But, after you go for a longer drive, once the brakes heat up, that’s where the discrepancies in the rotor are going to come up and cause brake pulsation.

Brake pulsation is usually caused by warped rotors, and it can be quite dangerous. If you feel your brakes pulsating, it’s important to have them checked out as soon as possible. Warped rotors can cause your brake pads to wear unevenly, and they can also lead to premature brake failure.

Can Air In Brake Lines Cause Pulsating?

Can Air In Brake Lines Cause Pulsating (Answered!)

No. While air in brake lines can lead to serious braking problems, it is generally not the direct cause of brake pedal pulsation, which is typically caused by unbalanced or warped rotors or brake discs

This phenomenon is generally attributed to unbalanced or warped rotors or brake discs.

While trapped air can lead to other serious braking issues by interfering with the pressure buildup, it does not directly result in a pulsating feeling when braking.

Hence, while it’s essential to address the issue of air in brake lines, brake pedal pulsation typically has different underlying causes.

What Causes Air In Brake Lines?

  • Improper bleeding of the brake system: If the brake fluid isn’t properly bled after maintenance, air can get trapped in the brake lines.
  • Leaks in the brake line or system: Any cracks or punctures in the brake line can let air enter the system.
  • Low brake fluid level: If the brake fluid level is too low, air may enter the master cylinder and subsequently the brake lines.
  • Faulty brake line components: Worn out or damaged seals, valves, or other parts in the brake system can allow air to infiltrate the brake lines.
  • Poor maintenance and neglect: Over time, without proper care and regular maintenance, the brake system can develop conditions that allow air to enter the brake lines.

Will Air Work Itself Out of Brake Lines?

Air will not work itself out of brake lines on its own. You’ll need to bleed the brakes in order to get rid of any air that may be trapped in the lines. This is a pretty simple process that can be done at home with the help of another person.

Air in the brake lines is a serious problem that can lead to decreased braking performance or complete failure of the brakes. There are several ways that air can enter the brake lines, including leaks in the master cylinder, wheel cylinders, or calipers; cracks or holes in the brake hoses; or incorrect bleeding of the brakes.

Any of these problems can cause the brakes to feel spongy when applied or may cause the brake pedal to sink to the floor. In extreme cases, the air in the brake lines can cause the brakes to lock up or fail completely.

Brake fluid should be flushed every two to three years because it’s hygroscopic. Meaning it likes to absorb water. The problem with water in the brake fluid is when water gets in the brake master cylinder, water has a really low boiling point.

Compared to brake fluid the boiling point could be 400 degrees, but water’s boiling point is 212 degrees Fahrenheit. So, it’s not very high and the brakes get hot and they could easily exceed 200 degrees Fahrenheit.

If that happens and you have a lot of water in your brake fluid, the water will vaporize and boil creating a void(air). When you press on the brake, that void is compressible and it’ll feel like you don’t have any brakes says Way.

Can Air Get Trapped in Master Cylinder?

Yes, air can indeed get trapped in the master cylinder, as well as other components of a vehicle’s hydraulic system, which may lead to braking issues if not properly addressed.

The master cylinder is the heart of your vehicle’s braking system. When you press your brake pedal, it distributes brake fluid through hydraulic lines to the four wheels of your car. Anytime a hydraulic braking component is replaced, air will get trapped in the master cylinder and that can cause a spongy pedal and reduce braking performance. 

The brake master cylinder is an important component of a vehicle. Brake master cylinders convert the force of the foot or fingers into hydraulic pressure.

The master cylinder is a foot-operated pump that forces fluid to the brake lines and wheel cylinders to stop a vehicle.

As the driver presses the brake pedal, the push rod pushes the first rubber piston cup over the compensating port and consequently, pressure builds up in the first brake circuit. As a result, the second rubber piston cup is moved over the second compensating port and pressure builds up in the second brake circuit.

When the air gets trapped in the master cylinder, bleeding the brakes is needed.

How To Fix Air Trapped In Brakes

  • Identify the problem: Inspect the brake system for any leaks or damage that could be allowing air into the lines.
  • Gather necessary tools: You’ll need a wrench, a clear tube, a container for old brake fluid, and new brake fluid.
  • Bleed the brakes: Attach the clear tube to the bleeder screw (found behind each wheel), and place the other end of the tube into a container. Loosen the screw slightly, then have someone press the brake pedal. This will force out the brake fluid, along with any trapped air. Tighten the screw before the brake pedal is released to prevent air from re-entering.
  • Repeat the process: Do this for all wheels, starting with the one furthest from the master cylinder and moving closer.
  • Refill the brake fluid: After all the air is removed, ensure to refill the brake fluid in the master cylinder to its proper level with new, manufacturer-recommended brake fluid.
  • Check your work: Once you’ve bled the brakes and replaced the fluid, test your brakes to make sure they’re working correctly. If not, you may need to repeat the process or seek professional help.


Q: How does air get into brake lines?

A: Air can enter brake lines through various ways, such as a brake fluid leak, improper bleeding procedures, or a damaged brake hose or line. It is important to regularly inspect your brake system and address any issues to prevent air from entering the lines.

Q: What are the symptoms of air in brake lines?

A: Some common symptoms of air in brake lines include a soft or spongy brake pedal, increased brake pedal travel, longer stopping distances, and pulsating or vibrating brakes. If you experience any of these symptoms, it is recommended to have your brake system inspected by a professional.

Q: Can I drive with air in my brake lines?

A: It is not recommended to drive with air in your brake lines. Air in the brake lines can affect your braking performance and compromise your ability to stop safely. It is best to address the issue promptly and have your brake system inspected and repaired by a professional.

Q: How often should I bleed my brake lines?

A: The recommended frequency for bleeding brake lines can vary depending on various factors, such as the type of vehicle and driving conditions. As a general guideline, it is recommended to have your brake lines bled every 2-3 years or whenever you notice symptoms of air in the brake system.

Q: Can air in brake lines cause brake failure?

A: While air in brake lines may not directly cause brake failure, it can significantly compromise your braking performance. Air can result in a loss of brake pedal feel, reduced braking power, and an increased stopping distance. It is important to address any issues with air in the brake lines to ensure your brakes function properly.

Q: What causes a spongy brake pedal?

A: A spongy brake pedal is often caused by air in the brake lines. When air is present, it can compress more easily than brake fluid, resulting in a soft or spongy feeling when you apply the brake pedal. Other possible causes include a worn or damaged brake master cylinder or issues with the brake calipers or wheel cylinders.

Q: Can I bleed my own brake lines?

A: While bleeding brake lines can be done as a DIY project, it requires some knowledge and the right tools. If you are not comfortable or familiar with the process, it is recommended to have a professional technician perform the brake bleeding to ensure it is done correctly.

Q: How can I prevent air from entering my brake lines?

A: To prevent air from entering your brake lines, it is important to maintain your brake system properly. Regularly inspect the brake hoses and lines for any signs of damage or leaks. When performing brake repairs or maintenance, ensure you follow the proper bleeding procedures and use the correct brake fluid specified for your vehicle.

In Conclusion

When it comes to the question of whether or not air in brake lines could cause pulsating brakes, the answer is a definite yes.

Air bubbles can cause an uneven distribution of pressure that would lead to a pulsating effect when the brake pedal is pressed.



Vide Polowenski, Senior Mechanic

The information in this article is current and up-to-date in accordance with the latest mechanic SOPs.

Please take the time to leave a comment if this article has helped you in any way, you need additional help, or you have a suggestion.

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