Why does the brake suddenly become soft?
3 Answers
The reasons for the brake becoming soft are: Air in the brake line: Brake fluid is the medium for transmitting force in the braking system. If air enters the line, the brake fluid under high pressure will appear insufficient in strength; Brake fluid not replaced for a long time: If the brake fluid is not replaced in time, it will contain excessive impurities and moisture; Oil leakage or overly soft brake material: Generally, oil leakage from the brake master cylinder or brake line will cause the vehicle's brake to become soft. The brake is a mechanical braking device that can slow down the speed, also known as a decelerator. The car's brake pedal is located under the steering wheel. Pressing the brake pedal causes the brake linkage to be pressurized and transmitted to the brake shoes on the brake drum, clamping the brake disc to slow down or stop the car.
A few days ago, my car had the same issue—the brake pedal felt spongy when pressed, which was really scary. I checked it myself and found that the brake fluid was more than half gone, probably due to a small leak in the pipeline. Brakes rely entirely on hydraulic pressure, and without it, the pedal becomes extremely soft. Another common cause is air entering the system, especially if bleeding wasn’t done properly after maintenance, making the brakes feel weak when driving. I immediately pulled over and didn’t dare to continue, fearing an accident. Later, I called a repair shop, and they replaced the brake fluid and seals, fixing everything. If you encounter a similar situation, I suggest not pushing your luck—stop and check the fluid level and for leaks first. Safety comes first. If air gets into the system, it needs to be bled again, which isn’t something you should attempt yourself—leave it to professionals for peace of mind. Regularly changing the brake fluid, about every two years, can prevent this issue.
I feel that spongy brakes are the most dangerous and must be addressed immediately. It could be due to low brake fluid or air in the system—air contamination can cause a longer pedal travel and slower response. Another possibility is severely worn brake pads or issues with the brake discs, but soft brakes are more often related to the hydraulic system. If the fluid reservoir is empty, there's an 80% chance of a leak, so you'll need to check the lines and calipers. At home, you can quickly check under the car for any fluid leaks. If the fluid level is below the 'min' line, don't drive the car. I tried simply topping up the fluid once, but the problem persisted—it turned out the master cylinder was faulty, costing a few hundred bucks to fix. In short, don't ignore small issues; safe driving relies on good brakes. Make it a habit to check the dashboard warning lights before driving to prevent major problems.
