What are the symptoms of a damaged brake master cylinder in large vehicles?

[DelEdward]

Here are the specific symptoms of a damaged brake master cylinder in large vehicles: Brake pedal not returning: The reason could be oil leakage in the brake master cylinder or wheel cylinder, or a malfunction in the master or wheel cylinder causing the pedal to sink. Additionally, it might be due to wear, lack of lubrication, or damage to the bearings on one of the axles. Damaged bearings can cause the entire vehicle to operate uncoordinated. If the brake pads are in an incorrect position, it can result in the brake pedal not returning. Brakes becoming too hard or too soft: It is normal for the brake pedal to be hard when the vehicle is stationary because the vacuum booster is not yet operational. However, if the pedal remains hard after starting the vehicle, it could be due to a vacuum hose leak or a damaged vacuum pump. Steering wheel pulling to one side during braking: During braking, it is difficult to detect uneven braking due to the high speed of the brake discs. However, when the vehicle is about to stop, the difference becomes more noticeable. The wheel on the side that stops first will cause the steering wheel to pull in that direction. This occurs due to an imbalance in the force applied by the left and right wheel cylinders on the brake pads, and the wheel cylinder should be replaced promptly in such cases.

[CharlesRose]

I've been driving heavy trucks for nearly ten years, and the symptoms of a failing brake master cylinder are quite obvious. The most noticeable sign is the increased pedal travel—normally stopping at half-pedal, but now requiring a much deeper press or even going to the floor for minimal braking effect, significantly reducing stopping power. Sometimes, the brakes feel spongy on the highway, extending stopping distances and nearly causing rear-end collisions multiple times. Brake fluid leaks may also occur; spotting oil stains under the hood or the fluid level warning light turning on should raise immediate concern. The safety risks are substantial, especially when fully loaded—insufficient braking uphill is downright terrifying. If you detect oil leaks or a weak pedal rebound during inspection, rush to a repair shop for a replacement. Delaying repairs too long can endanger the entire vehicle's safety.