What Causes Air Brake Rollaway?
2 Answers
Air brake rollaway indicates that the parking brake is not fully engaged or there is a malfunction with the parking brake. Here are the solutions for air brake rollaway: 1. Engage the parking brake firmly. If the parking brake cable is damaged, it is usually due to misalignment or deformation of the parking brake shoe bracket, resulting in reduced contact of the brake shoe. A detailed inspection is required, and it is advisable to visit a 4S shop for repairs as soon as possible. 2. The air brake system is commonly used in the parking brake systems of medium and large-sized vehicles. In such systems, a powerful spring maintains a constant braking state. When the vehicle needs to move, the driver releases the parking brake by performing an inflation action. A certain level of air pressure must be reached to push the spring open, thereby releasing the parking brake and allowing the vehicle to move.
When I was driving heavy trucks before, I also experienced the parking brake failing and the truck rolling. At that time, I was parked on a slope in the freight yard, and even with the handbrake pulled, the truck still rolled backward, almost hitting the container behind. Later, I had an experienced mechanic check it, and he said the return spring in the spring brake chamber was broken, causing the brake drum not to press tightly. Air line leaks are also a common issue, especially in older vehicles where rubber hoses age and crack, leading to insufficient air pressure and ineffective braking. The mechanics in our fleet taught me to listen for hissing sounds indicating air leaks and to check if the air pressure gauge needle is steady when parking. Now, before every long trip, I inspect the push rod travel of the brake chamber—if it exceeds the specified length, it means the gap is too large. These lessons were learned the hard way, and friends driving heavy trucks really need to pay attention to these details.
