Blog Car Care Advice Air in the Brake Lines: Symptoms, How It Happens & Fixes
Car Care Advice

Air in the Brake Lines: Symptoms, How It Happens & Fixes

Looking for a mechanic near you for maintenance or repair? AutoNation Mobile Service brings the shop to you. Get a free instant quote today.
Get a Quote

Do your brakes feel spongy and ineffective?

You might have air in your brake lines, which could lead to longer stopping distances and subsequent fender benders.

In this article, we’ll explore the symptoms of air in the brake line, how it happens, and how to fix it through bleeding brakes or alternative methods. We’ll also cover its seriousness and how to slow air buildup in your braking system.

This Article Contains:

Let’s begin.

Symptoms of Air in the Brake Line

These three symptoms can indicate the presence of air in the brake line:

Next, let’s explore how air enters a seemingly airtight brake system.

How Does Air Enter Brake Lines?

When air enters the brake lines, which house and circulate brake fluid, it reduces the pressure in the brake system, leading to ineffective braking. 

But how does air find its way into the brake line in the first place?
Here are a few ways it could happen:

1. Air Gets Trapped in Brake Fluid Reservoir

The brake fluid reservoir, which supplies each brake line with the brake fluid, may let air into the system.

Here’s how:

2. Water Enters the Brake Fluid

Brake lines require brake fluid that isn’t contaminated with water, dust, or dirt.
Here’s how water-contaminated brake fluid can introduce air pockets in your brake system:

So, what can you do to remove air from your brake system?

How to Get Air Out of Brake Lines: A Guide to Bleed Brakes

Bleeding brakes involves removing trapped air and old brake fluid using a batch of fresh fluid.

This process should be done correctly since your vehicle’s braking system is crucial to vehicle safety. So, it’s best to contact brake repair technicians if you’re unfamiliar with the bleeding brakes. 

Here’s what a mechanic would do:

  1. Jack the car on solid ground and ensure the brake lever is up.
  1. Remove the tires and locate the brake caliper assembly or drum brakes.
  1. Find the bleed screws (also known as the bleeder valve or bleeder bolt) for each wheel. The bleeder screw is usually found near the bottom of the brake caliper on a disc brake, and behind the backing plate, near the top, on drum brakes.
  1. Begin at the furthest brake from the master cylinder. Loosen the bleeder screw using a box wrench. Ensure that every other bleeder screw is tight to prevent air from entering the brake fluid.
  1. Ensure the brake fluid reservoir (a.k.a master cylinder reservoir)remains full at all times during the process. You can pour clean brake fluid into the reservoir periodically to maintain an adequate brake fluid level.
  1. Fit one end of a plastic hose over the first bleed screw. Attach the other end of the plastic hose to an empty bottle.
  1. Ask an assistant to apply the brakes several times and hold the brake pedal halfway to the floor.
  1. As they apply pressure, the mechanic would use the wrench to open the bleeder screw. This action will force the trapped air and old fluid out of the brakes.
  1. Repeat the process for each bleeder bolt, and make sure to top up the reservoir with fresh brake fluid.
  1. Monitor the fluid reservoir for slight movement when applying the brakes.
  1. Fasten the bleeder screws.

If bleeding your brakes fails to solve the issue, you may have other problems related to your brakes, like a damaged brake line or worn master cylinder.

What else can you do?

Alternative Methods to Remove Air in Brake Lines

Here are alternative methods a mechanic may try:

Having air in the brake line is worrying. Let’s explore why.

How Serious is Air in the Brake Line?

Unless your vehicle has an air brake system, air in the brake line is a serious issue that you should address ASAP.


When you apply pressure to the brake pedal, it acts as a lever that amplifies the power by up to six times. This pressure travels from the master cylinder, through the brake line, and acts on the brake caliper and brake rotor.

However, if air bubbles are in the brake line, hydraulic pressure is reduced, making your entire braking system less effective and your vehicle more difficult to control. This can lead to accidents, harming you and others around you.

Now, let’s see how you can slow down the buildup of trapped air in the brake line.

How to Slow Down Air Buildup in Brake Lines

Here are some tips to help slow down air buildup in the brake lines:

Final Thoughts

Having air pockets in your brake line has the potential to cause accidents and severely damage your beloved vehicle. You’ll need to bleed your brakes or use a vacuum pump to remove the air pockets. 

However, solving this issue takes work. So if you have spongy brakes, it’s easier to contact brake repair technicians to help bleed your brakes. 

Looking for reliable technician who offers braking system repair?
AutoNation Mobile Service is a convenient mobile auto repair and maintenance solution offering competitive, upfront pricing. 

Get in touch with us to have an expert mechanic assist you with brake bleeding, master cylinder replacement, and much more, right from your driveway!