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!)

Air in the brake lines can cause a number of problems, including reduced braking power, increased stopping distance, and even complete loss of braking ability. It is very unlikely that air in brake lines can cause pulsating. Brake pulsations are usually caused by unbalanced or warped rotors. The main cause of warped rotors is generally because of overheating.

The reason why your brakes might overheat is generally that either the cooling fins on the braking rotors are rotted on the inside and they’re not functioning the way they need to to be able to dissipate the heat, or maybe you have a sticking brake condition where your pads are just continuously applying brake pressure to the rotor, creating heat in excess of what the rotor can actually dissipate.

The most common place for you to have a brake pulsation is gonna be from the front brakes. The reason for that is because your vehicle’s gonna put the majority of the braking power to the front. With that said, the front rotors need to be much thicker than the rear rotors. They’re also gonna have cooling fins in them. The reason for that is because, as I said, they get the majority of the braking coming from the fronts, so they need to be able to dissipate the heat properly.

The rear rotors are gonna be much thinner than the front rotors. The reason for that is that the rear brakes are actually mostly for stabilizing the vehicle when you’re braking. They still need to brake a little bit because, of course. You don’t wanna just be braking with your fronts. Because then your vehicle’s gonna do a nosedive every time you step on the brakes.

Will Air Work Itself Out of Brake Lines?

Unfortunately, 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 its 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.

Can Air Get Trapped in Master Cylinder?

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.

Igor Iwanowski

I am a certified Automotive Service Excellence (ASE) mechanic since 2018. I specialize in Brake systems, dashboard warning lights, EGRs, general engine problems, EVAP and Emissions issues.

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