What Are the Common Causes of Soft Brakes in Trucks?
3 Answers
Here are several common reasons for soft brakes: 1. Air in the brake lines: Brake fluid is the medium that transmits force in the braking system. If air enters the brake lines, the brake fluid under high pressure will appear insufficient in force. Although braking force still exists, the maximum braking force is significantly reduced. In this case, the brake system should be bled at a repair shop promptly. To determine whether there is air in the brake lines, press the brake pedal several times with the engine off until the brakes feel firm. Then, hold the pedal down. If it remains firm, the system is normal. If the pedal slowly sinks, it indicates air in the brake system. 2. Long overdue brake fluid change: If brake fluid is not replaced in time, it will contain excessive impurities and moisture, which will affect the transmission of braking force. Therefore, brake fluid must be changed regularly, and a moisture content test should be performed at a repair shop if possible. 3. Oil leakage or overly soft brake materials: Generally, oil leakage from the master cylinder or brake lines will cause the vehicle's brakes to feel soft. Additionally, if the brake materials are too soft, their high-temperature stability will deteriorate, which can also lead to soft brakes in the vehicle.
I've been driving trucks for over a decade in the transportation industry, and I've encountered the issue of soft brakes several times. The most common cause is air getting mixed into the brake fluid, making the pedal feel loose and spongy, like stepping on cotton. Aging brake fluid absorbing moisture can also make it thin and ineffective. Damaged hoses or worn-out pump components leaking oil are also frequent problems, especially after long, bumpy journeys. I remember last time on a mountain road when the brakes suddenly became too soft to stop properly. Fortunately, with my experience, I managed to pull over in time to check and found the fluid was full of air bubbles. After bleeding the system, it worked much better. Regular maintenance is key—change the fluid periodically and conduct a thorough inspection every 20,000 kilometers. Don't wait for an accident to regret cutting corners—safety isn't where you should skimp to save money!
As an enthusiast who often helps fellow drivers troubleshoot minor issues, I'm quite familiar with the reasons for soft truck brakes: mainly air infiltration into the braking system, making the pedal feel soft and weak; or brake fluid being too old and contaminated, losing viscosity and effectiveness after absorbing moisture; hose expansion or rupture is also a common cause, especially without regular maintenance; wear of the master cylinder or leakage in the wheel cylinders can lead to pressure loss. When you notice soft brakes, stop the vehicle immediately and test the pedal response by pressing it multiple times. If it sinks, bleeding or part replacement is needed. Develop a habit of checking the fluid level and condition every six months. Change discolored fluid immediately and tighten any loose components promptly. Simple maintenance can prevent major problems!
