What are the causes of soft brakes in trucks?
2 Answers
Here are some common reasons for soft brakes: 1. Air in the brake lines: Brake fluid is the medium for transmitting force in the braking system. If air enters the brake lines, the brake fluid under high pressure will appear insufficient, resulting in a noticeable reduction in maximum braking force despite some braking power remaining. In this case, the brake system should be bled at a repair shop as soon as possible. To determine if there is air in the brake lines, press the brake pedal several times with the engine off until it becomes hard. Then, keep the pedal pressed. If it remains hard, the system is normal; if the pedal slowly sinks, it indicates air in the brake system. 2. Long overdue brake fluid replacement: If brake fluid is not replaced in time, it may contain excessive impurities and moisture, which will affect the transmission of braking force. Therefore, brake fluid must be replaced regularly, and it is advisable to test its moisture content at a repair shop when possible. 3. Oil leakage or overly soft brake material: Generally, oil leakage from the master cylinder or brake lines can cause soft brakes. Additionally, if the brake material is too soft, its high-temperature stability will deteriorate, also leading to soft brakes.
I've been driving trucks for over a decade and often encounter soft brake issues, where the pedal feels spongy and braking performance is poor. The main causes include insufficient brake fluid or leaks, air bubbles in the lines requiring bleeding, aging and swelling of brake hoses that lose effectiveness over time, excessively worn brake discs or thin brake pads affecting responsiveness, faulty master cylinders causing uneven pressure distribution, and low tire pressure or misaligned systems indirectly contributing to soft brakes. I remember once during a long-haul downhill drive when the brakes went soft, nearly causing a rear-end collision—it was terrifying. It's crucial to regularly check brake fluid levels and lines, and address any issues immediately at a repair shop—never cut corners on safety. Safety comes first; never push through with faulty brakes, especially with heavy loads where risks are higher.