What to Do If There's Always Air in the Brake System?

[VanSamuel]

The correct method to bleed air from the brake system is as follows: 1. Press the brake pedal 5 to 6 times consecutively. 2. Keep the brake pedal pressed, immediately loosen the air bleeder screw on the wheel brake caliper, then quickly tighten it. 3. Repeat this process until the brake fluid shoots out in a straight line from the air bleeder screw. Precautions for bleeding air are as follows: 1. When bleeding air, follow the sequence of right rear wheel, left rear wheel, right front wheel, and left front wheel. 2. The discharged brake fluid should not be reused, as brake fluid that has been in prolonged contact with air absorbs moisture, which can affect the vehicle's braking performance.

[McAnastasia]

I've encountered a similar issue before where the brake bleeding was never thorough, most likely due to a problem with the brake master cylinder. There might be aged or worn seals inside the master cylinder, allowing air to continuously seep in—air gets bled out, but new air keeps entering. In such cases, the first step is to inspect the master cylinder for any oil leaks or unusual noises. If the master cylinder is confirmed to be damaged, the only solution is to replace it, as further bleeding won't help. When driving on highways, if the brake pedal feels soft and there's a delayed stopping response, it's extremely dangerous. When I experience this, I immediately head to a professional repair shop. Technicians there will use instruments to check the pressure, ensuring everything is safe. The braking system is a matter of life and death, so never attempt DIY fixes recklessly—it's much more reassuring to spend some money on professional repairs. Adding fresh brake fluid during regular maintenance can prevent similar failures, especially for older vehicles, which require extra attention in this regard.

[McLayla]

As a seasoned driver with years of experience, I've encountered the issue of air in the brake system. Once, I tried bleeding the brakes by the roadside myself, but it felt like the air wasn't completely purged no matter how many times I tried. Later, I discovered that the bleeder valve on the rear brake was loose, allowing air to seep in. The correct method requires two people to cooperate: one sits in the car and pumps the brake pedal while the other loosens the bleeder screws on each wheel, starting from the wheel farthest from the master cylinder (e.g., rear to front), and stops only when fresh brake fluid without bubbles comes out. During the process, keep an eye on the brake fluid reservoir level—top it up with new fluid if it gets too low to prevent air from being sucked back in. If the brake fluid is old and contaminated with impurities, it can also cause bubbles. I recommend replacing it with a high-quality brake fluid, which usually solves the problem. Safety comes first—brake failure is no joke.

[SanCarter]

Last time my car had the same issue, the brake kept getting air in it no matter how many times I bled it, which was really frustrating. Simply put, the problem might be with the connecting lines or a poor seal, like a loose fitting or a tiny crack in the brake line, allowing air to sneak in. After trying a few times without improvement, I took the car to my trusted mechanic. The technician helped inspect the entire system, focusing on the lines and the brake pump, and fixed it in ten minutes. Don’t underestimate this air issue—it can increase braking distance while driving, making accidents more likely on sharp turns or slopes. If all else fails, top up the brake fluid as a temporary fix, but get it properly handled as soon as possible to save both hassle and money.

[OLaura]

When I first started learning car repair, I was also troubled by this issue. There was always residual air when bleeding the brakes, and it felt like a waste of effort. Later, I understood that the reasons could be incorrect operation or a system leak. To bleed the air properly, ensure the fluid reservoir is filled to the marked line. Before loosening the bleeder valve each time, pump the brakes a few times to build pressure, then bleed. Repeat this two or three times for each wheel. If working alone is inconvenient, use the two-person method by having a friend pump the brakes for you. The bleeding sequence should start from the wheel farthest from the master cylinder, such as the right rear wheel, then the left rear wheel, followed by the front wheels. Doing it wrong will leave air trapped. It's advisable to try new brake fluid, as old fluid containing moisture can expand when heated, creating bubbles that are hard to remove. Don’t overlook small issues; get them fixed properly at a professional shop for peace of mind.

[McMiranda]

Why is there always air in the brake system that can't be fully bled? I believe the root cause lies in the source issues. Brake fluid absorbs moisture over time, forming bubbles under high temperatures, which reappear after bleeding. When changing the fluid, always use high-quality, manufacturer-certified fluid, and it's best to check the fluid condition annually. Additionally, aging system components like the master cylinder or hoses can lead to poor sealing, allowing air to seep in—carefully inspect every connection point. I once experienced ineffective rear brake bleeding, only to discover a faulty oil pump; replacing it solved the problem completely. If you notice a loose brake pedal or unusual noises while driving, stop immediately for inspection—don't risk driving further. Regular maintenance, including frequent fluid changes, helps minimize such issues.