What is the problem if the air pressure of the parking brake drops quickly?
3 Answers
If the air pressure of the parking brake drops quickly, it indicates there is air leakage in the air reservoir or air pipes. If there is no leakage after the engine is turned off, it is normal pressure release. Method for bleeding the brake system: First, two people need to cooperate to avoid mistakes. One person is responsible for pressing the brake pedal 4-5 times, while the other person loosens the bleeder screw on the brake caliper. If there is indeed air in the brake lines, some brake fluid and gas will be expelled. Repeat the above steps until only brake fluid comes out, indicating that all the air in the brake lines has been removed. Finally, tighten the bleeder screw to complete the process. Definition of drum brakes: Simply put, drum brakes are braking devices that use stationary brake shoes inside the brake drum to create friction against the rotating brake drum, thereby reducing the wheel's rotation speed.
I encountered a rapid air pressure drop during a long-distance trip recently. After pulling over to check, I found the exhaust valve on the air reservoir was leaking. If this component isn't properly sealed, the pressure plummets fast. Those air line connectors also need careful inspection, especially at the tractor-trailer connection points where rubber hose aging and cracking are common. A failed air dryer can be troublesome too - whether from moisture clogging pipes or stuck exhaust valves affecting pressure. The most annoying was discovering a torn brake chamber diaphragm - you'd hear hissing with every brake application. That time I spent hours soap-testing every joint before finally locating a cracked relay valve diaphragm. My advice: always test pressure drop rate after parking - anything exceeding 0.1 kg per minute indicates problems.
Having worked in auto repair for over a decade, I've handled numerous cases of air brake system leaks. The most common issue is air circuit leakage, where any part of the pipeline from the air compressor to the brake valve can develop problems. Particularly in winter, rubber hoses harden and connections loosen after just a few bumps. Once, a customer's four-circuit protection valve got stuck, causing air pressure to drop from 8 kg to 4 kg in just three minutes. Aged cups in spring brake chambers are even more dangerous—when releasing the brake, the leaking air sounds like a snake hissing. I recommend using a pressure gauge to test each air reservoir's pressure retention and isolating circuits for troubleshooting. Don't forget to check the dryer's exhaust port—continuous leakage indicates internal valve failure. Areas with heavy grease buildup on pipelines are 80% likely to have cracks.
