Air in Brake Line – Common Signs & Useful Solutions | Autance

The safety of your car depends on the sharp brakes. But when you are driving your car and you step on the pedal, you feel it is soft or spongy. This is one of the signs of air in brake line. You should know that the brake line is an integral part of the brake system…

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Air in Brake Line – Common Signs & Useful Solutions | Autance © Air in Brake Line – Common Signs & Useful Solutions | Autance

The safety of your car depends on the sharp brakes. But when you are driving your car and you step on the pedal, you feel it is soft or spongy. This is one of the signs of air in brake line.

You should know that the brake line is an integral part of the brake system responsible for turning pedal action into stopping force. Most automobiles have a unique hydraulic system; thus, it uses brake fluid stored by master cylinder to transmit stopping power to the brakes from the foot. But first…

What is a Brake Line?

This is part of the brake system responsible for circulating the fluid. And it uses excess pressure from the fluid to power your car brakes. It allows your vehicle to turn the pressure from the foot pedal to stopping force. 

Most vehicles’ brake system uses it to transfer excess pressure to the brakes. The master cylinder, which stores the fluid, transfers it to the calipers through brake lines. In turn, the calipers compress the car brakes, thus slowing it down and finally stopping your vehicle.

Symptoms of Air in Brake Line

Air is the worst enemy in the brake system because it reduces the force exerted, thus making the process relatively ineffective. The hydraulic system suffers if it gets into your car’s line. The following are the air in brake line symptoms;

Spongy brake Pedal

 It greatly depends on the fluid to function correctly. When you compress the pedal, it transfers the hydraulic force to the calipers, which in turn press the pads into the rotors to stop or slow down your car.  

The fluid is denser than air. Therefore, the air in brake line can be compressed easily; and, you can start feeling your brakes become spongy. Hence, your vehicle can neither stop nor slow down due to the sponginess.

Soft Brakes

The main reason your brakes are soft is because of the air in the lining system which can cause pressure imbalance. And the system greatly depends on the hydraulic pressure to stop the vehicles. You must understand that insufficient pressure leads to a soft pedal.

And, the air in brake line can be due to leakage or a low amount of brake fluid. You can diagnose this problem by gently pumping the pedal several times to make it steady.  

Depressed Brake Pedal

When the hydraulic system is incredibly effective, you can feel the power of the pedal if you compress it with your foot. But, if you notice that it is loose and returns abruptly after removing your foot off it, then it’s an indication that your brake line is filled with air.

The depressed pedal is too close to the floor of the car due to the damaged master cylinder. Therefore, it is dangerous to drive a vehicle with a damaged pedal because it is very risky. Seek professional assistance to solve this problem as soon as possible.

Techniques of Bleeding the Brakes

To enhance the condition of your hydraulic system, you should remove the air in brake line. You can do this job by yourself, or you can seek the assistance of a professional mechanic. There are various ways you can bleed your car brakes.


The main idea is to create a vacuum to draw some air and fluid from the bleed screws into a container. You can use a vacuum gun with all bleeding attachments and equip with a new vinyl tubing. First of all, you should attach the screw adapter, connect the tubes and small containers for catching the fluid and air. 

Then pull to create some great vacuum and fissure the bleeding screws. This method is sometimes challenging because air can get around the threads, thus creating bubbles in the tubes. To prevent deceptive bubbles, you can slather heavy-bearing oil around the screws.

Hold and Pedal

Sometimes gravity can be less effective and does not hold. This is where the technique of using two people comes in. One person is in the driver’s seat while the other person is responsible for closing and opening the screws.

The person in the car exerts pressure, while the other one holds the container as bleeding continues. Repeat this process as you embrace the call-outs such as “apply pressure, hold down and stop” to speed it up. Therefore, the two-person technique is an effective method to use in eliminating it.


This is the simplest method, and you can do it by yourself. All you need to do is to fix a transparent tube onto the bleed screw and open it. Remove the air from the brake line, and watch out fluid ooze out too. The small bottle prevents from drying your reservoir. 

The magnet also holds it firmly, and you might notice sudden changes in the fluid flow into it. The bottle can be overflowing one minute and empty after some time. So, you need to be very careful with gravity.

Pressure Reservoir

You should use this method because you can push all the air molecules and expired fluid because it is the best technique. There are several pressure tanks in the market. Nevertheless, the concept of getting air out of brake lines is the same.

Check the amount of pressure in the tank and any possible leakages in the master cylinder, and depressurize it. Fill the reservoir with fluid and pressurize it. Crack the screws using the wrench to bleed out the fluid and air in a catch container.

You can also use a universal round cap or adapters that fit directly. Moreover, the bleeder can also sort out the modulator effectively. All these mechanisms are quite compelling; you can choose the best one that suits you.

How to Get Air Out of Brake Line?

The fluid is designed to last for a long time before you replace it. After a while, it loses the ability to resist moisture. In addition, it starts to absorb some air and water, thus reducing the performance of the brakes.

The best way to replace it is through bleeding the hydraulic system. It means eliminating air and old fluid from the system. Bleeding is straightforward to achieve at home, and here is how you can do that in quick steps.

Step #1: Choose the Best Fluid

You should consult the manufacturer’s manual to know the exact types of brake fluid your car requires and the intervals it should be replaced. Therefore, go to the nearest car shop and purchase the best brake fluid of about 14-ounces to bleed the hydraulic system. You can now go ahead and lift your car.

Use a jack to lift your car on level ground, particularly in your driveway. Use robust jack stands to support it firmly on the ground. The bleeding process requires you to climb gradually under it in intervals. You should remove all the wheels. 

Step #2: Locate the Bleeder Screws

After removing the tires, you can quickly locate the screws. Gently loosen them, and if they prove tough, apply a small amount of oil. After that, you need to bleed each of them by twisting them up slightly.

Ensure that the system doesn’t suck in the air which is the greatest enemy of the brake system. They can make the pedals feel spongy and soft, thus reducing their performance. You should be very careful while conducting this process.

Step #3: Check the Level of the Fluid

You should also ensure fluid in the engine compartment is ¼-inch full. And also, ensure that you purchase the right one. Therefore, during the bleeding process, you should leave the cap of the master cylinder open.

You should bleed each brake line at the proper sequence. Read your manual to understand which one should be first to be bled. But, it is imperative, to begin with, the one that is far away from the master cylinder, and in most vehicles, it is the rear right tire.

Step #4: Apply Pressure on the Brakes

Tightly attach a long clear tube over the screw hole of the first brake you will be bleeding, and place the other end in a container, especially a plastic bottle. The long tube prevents the confined air from sneaking back into the line.

This is the step that you need assistance too. But you should ensure that the engine is off. Allow your assistance to pump the pedal for numerous strokes till they feel some compact resistance on your foot. They should maintain the pressure applied for quite some time.

Step #5: Bleed Off the Air and Fluid

As your helper keeps applying the pressure, open the screws slightly and allow them to pass through the transparent tube. Your helper will start to feel the pedal drop to the floor. Therefore, your assistance should inform you if it touches the floor.

Before releasing the pressure, you should tighten the screws. If you do this after your assistance releases the pressure, there are high chances of air sneaking back into the line. Therefore, you should be very cautious during this process and repeat steps 5 and 6 until you remove all the bubbles.

Step #6: Top Up the Fluid

As you work, ensure that you replenish the fluid to a ¼ -inch between your car tires. Fill the master cylinder reservoir with it up to the correct level. After bleeding all four brakes, let your helper apply pressure on the pedal and release it abruptly. Repeat the procedure until you are sure all the air is eliminated. 

Double-check to ensure that all the bleeder screws are very tight before you reinstall the tires. You can remove all the bubbles from the hydraulic system if you do this process correctly. Hence, you will have solid brake and great confidence while driving on the road.

Frequently Asked Questions (FAQs)

Is it possible for air to get into my brake lines? If yes, how?

Yes, air can sneak into your brake lines without you noticing. Most modern vehicles have incredibly air-tight systems. Unfortunately, air can penetrate the line due to the wear and tear of the pads. Moreover, the calipers also extend, thus maintaining a constant distance.

The pistons also extend, thus creating a void in the brake system; hence you need to supply it with more fluid. You should also monitor it closely so that the system can depress the pads. If your brakes are soft or spongy, then it’s due to air in the brake lines.

How can I know that my brake line contains air?

Air is the greatest enemy in the brake system, and when it gets into the lines, it becomes faulty and suffers greatly. Air bubble in brake line symptoms is an indication that brakes are weak and damaged. Other symptoms include soft or spongy pedal and depressed brakes.

Therefore, if you notice any of these warning signs, you should take your car to a professional mechanic to remove the air, or you can do it yourself at home. Remember that driving a vehicle with damaged brakes can be quite risky.

What can I do if my brake lines are damaged?

If you notice that they are broken or corroded, you should seek assistance from a professional. You can also remove the damaged line and replace it with a new one. Consequently, you should refill your master cylinder with fresh fluid.

In addition, you should inspect your line constantly to prevent further damages. Thus, you can protect other passengers, especially your family, while on the road. You need to do what is necessary for your safety.

ConclusionAir In Brake Line

To maintain the excellent condition of your hydraulic braking system, you need to remove air in brake line. You can do this job by yourself using any of the methods such as pressure reservoir, venture bleeder, vacuuming, use of gravity, or holding the pedal. In addition, you can follow the systematic steps described above to eliminate air.

You can also seek the help of a certified mechanic to do the job for you. The technicians can deprive your system of air. This enhances the stopping ability of your car and the prime safety while driving. You can need an electric current brake controller mounted on your vehicle to assure the brakes on the caravan work.

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