What Causes a Truck's Air Brake to Lose Air After a Few Presses?
2 Answers
It is caused by air leakage in the wheel cylinder pipelines or valve bodies. Below are specific details about air brakes: 1. Principle of air brakes: Also known as exhaust brakes, air brakes serve as an auxiliary braking system and cannot replace service brakes. A regulating valve is installed on the engine's exhaust pipe, and by closing this valve, the exhaust stroke pressure is increased, utilizing the generated negative pressure to obtain braking force. 2. Function of air brakes: Their purpose is to reduce or maintain vehicle speed without or with minimal use of service brakes, but they cannot bring the vehicle to an emergency stop. 3. Usage of air brakes: When the exhaust brake is engaged, the accelerator pedal is at zero position, and the fuel injector stops injecting fuel. If the accelerator or clutch pedal is pressed, the exhaust brake will automatically disengage, preventing engine stalling during stops and avoiding exhaust brake activation during fuel injection.
As a truck driver with over a decade of highway experience, I've personally encountered situations where the air brakes lose pressure after just a few pumps, which is truly nerve-wracking. Common causes include leaks in the air pressure system, such as ruptured aging rubber hoses or worn sealing rings at connections, leading to gradual air seepage. Inefficient air compressors can also be an issue—if they pump too slowly or fail entirely, the system pressure can't recover. I remember one time on the highway when the brakes went soft after a few presses, but thankfully I pulled over in time to inspect. My advice: first check the pressure gauge readings—if they drop rapidly, start tracing the leak. Don’t overlook problems with the air reservoir either, as tank corrosion or valve malfunctions can worsen pressure loss. Never delay fixing such issues; get them resolved at a proper repair shop to avoid compromising road safety.
