What Causes the Hard Brake in JMC Shunda?
2 Answers
The main reasons for a very hard brake can be categorized into two scenarios. Here are the relevant details: 1. Vacuum Booster Pump: The vacuum booster pump may be leaking air or malfunctioning. It's important to note that the force applied to the brake pedal is amplified by the brake booster pump. If it fails, braking becomes more difficult, meaning you now rely solely on your foot's strength instead of the vacuum force from the brake booster pump, and the difference is easily noticeable. 2. Brake Booster Pump: Pressing the brake after the engine has been turned off is also related to the brake booster pump. The brake booster pump continuously generates vacuum only when the engine is running. When the engine is off, it relies on the residual vacuum assistance, which typically depletes after a few presses. However, this condition is not a malfunction and will restore once the engine is restarted.
I often encounter hard brake issues when driving my JMC Shunda for transportation, and there are several common reasons behind this. The main culprit is usually a faulty vacuum booster, the component that assists you in pressing the brake. If it leaks air or the diaphragm is damaged, the vacuum pressure becomes insufficient, making it extremely hard to press. Another reason could be air in the brake fluid or the fluid aging and deteriorating, causing poor force transmission in the hydraulic system. I remember once feeling nothing when driving empty, but when fully loaded, the brake was so hard it couldn't be pushed. Upon inspection, air was found in the brake line. Not addressing this promptly can lead to dangerously longer braking distances, especially on slippery roads during rain or snow. It's advisable to regularly check the vacuum valve and pipeline seals and replace the brake fluid. Professional repair shops can use equipment to bleed the brakes and test vacuum levels—don't delay. For workhorses like the JMC Shunda, which endure heavy-duty operations, problems accumulate quickly, so maintenance cycles should be shortened.
