What Causes the Brake Pedal to Suddenly Become Hard and Unpressable While Driving?

[DelAnna]

Brake suddenly becoming hard is generally caused by issues with the brake booster pump, foreign objects adhering to the brake pads and calipers, or the vehicle's ABS system intervention. Below is relevant information: 1. Issues with the brake booster pump: If the brake pedal suddenly becomes hard while driving, it may be due to a vacuum tube leak or blockage in the brake booster pump. In this case, the vehicle should be stopped immediately for inspection, and replacement may be necessary. 2. Related to braking before engine shutdown: The vehicle's braking system operates at its maximum efficiency when the engine is running, with the brake booster pump being the key component that amplifies the force applied to the pedal to achieve vehicle braking.