DYI Troubleshooting and Fixing Air in Your Brake Line: A Comprehensive Guide

by | Apr 14, 2023

Learn how to identify, diagnose, and resolve air in your brake line for optimum vehicle safety and performance

Air in the brake line is a common and potentially dangerous issue that affects a vehicle's braking system. It can compromise the safety and performance of your car, leading to longer stopping distances and reduced braking power. In this comprehensive guide, we will discuss the causes, symptoms, and solutions for air in the brake line, helping you maintain optimum vehicle safety and performance.

Understanding the Brake System and Hydraulic Fluid

Before we delve into the issue of air in the brake line, it's essential to understand the role of the brake system and hydraulic fluid in your vehicle. The brake system consists of several components, including the brake pedal, master cylinder, brake lines, calipers, brake pads, and rotors. When you apply pressure to the brake pedal, hydraulic fluid is forced through the brake lines, causing the calipers to squeeze the brake pads against the rotors, which in turn slows down the vehicle.

Hydraulic fluid, also known as brake fluid, is a non-compressible liquid that transfers force from the master cylinder to the brake calipers. It is essential for the proper functioning of the braking system, as it ensures consistent and efficient transfer of force. Air, on the other hand, is compressible and can negatively impact the performance of your braking system.

Causes of Air in the Brake Line

There are several reasons why air can enter the brake line, compromising the efficiency of your braking system:

  1. Leaky brake lines or components: Damaged or corroded brake lines, calipers, or other components can allow air to enter the system, displacing hydraulic fluid and creating air pockets.
  2. Improperly bled brakes: If the brakes are not bled correctly after maintenance or repair, air may remain trapped in the system.
  3. Low brake fluid levels: Insufficient brake fluid in the master cylinder can cause air to be drawn into the brake lines when the brake pedal is pressed.
  4. Worn or damaged seals: Deteriorated seals in the master cylinder or calipers can allow air to enter the brake system.

Identifying Symptoms of Air in the Brake Line

Air in the brake line can manifest in several ways, affecting the performance of your braking system. Here are some common symptoms to watch out for:

  1. Spongy or soft brake pedal: A spongy or soft brake pedal indicates that there is air in the brake line, as the compressibility of the air reduces the force transmitted through the hydraulic fluid.
  2. Longer stopping distances: Air in the brake line can cause your vehicle to take longer to come to a complete stop, as the braking force is diminished.
  3. Inefficient braking: If your brakes feel less effective than usual or require more pressure to slow the vehicle down, air in the brake line may be the culprit.
  4. Brake pedal sinking to the floor: In severe cases, the brake pedal may sink all the way to the floor when pressed, indicating a significant amount of air in the brake line.

Fixing Air in the Brake Line: Bleeding the Brakes

The most effective way to remove air from the brake line is through a process called brake bleeding. This involves forcing hydraulic fluid through the brake lines to expel any trapped air. Here are the steps to bleed your brakes:

  1. Gather necessary tools: You will need a wrench, a clear plastic hose, a container for collecting old brake fluid, and fresh brake fluid.
  2. Locate the bleeder valve: Find the bleeder valve on your brake caliper. It is usually a small nipple-like valve with a rubber cap, located near the brake pads.
  1. Prepare the bleeder valve: Remove the rubber cap and attach the clear plastic hose to the bleeder valve, ensuring a snug fit. Place the other end of the hose in a container to collect the old brake fluid.
  2. Top off the master cylinder: Open the hood and locate the master cylinder, which is typically near the firewall on the driver's side. Unscrew the cap and fill the reservoir with fresh brake fluid, ensuring it remains full throughout the bleeding process.
  3. Pump the brake pedal: Have an assistant pump the brake pedal several times and then hold it down firmly. This will build pressure in the brake system.
  4. Open the bleeder valve: While your assistant continues to hold the brake pedal down, use a wrench to open the bleeder valve slightly. Old brake fluid and air bubbles will flow out through the clear plastic hose and into the container. Once the flow stops, close the bleeder valve.
  5. Repeat the process: Continue the process of pumping the brake pedal and opening the bleeder valve until no more air bubbles appear in the clear plastic hose. Be sure to keep an eye on the brake fluid level in the master cylinder and top it off as needed.
  6. Bleed all wheels: Repeat the bleeding process for each wheel, starting with the one furthest from the master cylinder and working your way closer. This ensures that all air is removed from the brake lines.
  7. Check the brake pedal feel: After bleeding all the wheels, pump the brake pedal a few times to ensure it feels firm and responsive. If the pedal still feels spongy, repeat the bleeding process until the issue is resolved.
  8. Dispose of used brake fluid: Properly dispose of the old brake fluid according to your local regulations, as it is a hazardous material.

Preventing Air in the Brake Line

To prevent air from entering your brake lines in the future, follow these maintenance tips:

  1. Regularly check brake fluid levels: Ensure that the brake fluid reservoir in the master cylinder is always filled to the recommended level to prevent air from being drawn into the system.
  2. Inspect brake lines and components: Regularly check your brake lines, calipers, and master cylinder for signs of damage, corrosion, or leaks. Replace any damaged or worn components as needed.
  3. Change brake fluid periodically: Brake fluid can absorb moisture over time, which can lead to corrosion and air entering the system. Follow your vehicle manufacturer's recommendations for brake fluid replacement intervals.

By following these guidelines and addressing any issues with air in the brake line promptly, you can ensure the safety and performance of your vehicle's braking system.