What does it mean when the braking pedal sinks down when you start the engine as you press the pedal?
Show the correct answer
Correct answer
A. That the power brake system is working.
Explanation
In the photo you can see the pedals of a car, and a red arrow shows the brake pedal moving down. If you start the engine after pressing the brake pedal and the pedal "drops" slightly, this shows that the brake assistance (power brakes) is working - answer A. This effect has nothing to do with the fluid level in the reservoir (B) or with ABS (C).
In a typical car the brake assistance works thanks to the vacuum produced by the running engine. When the engine is not running, the pedal is hard; after you start the engine, the vacuum begins to assist the pressure of your foot and the pedal goes down a little deeper - this is a simple test of whether the brake servo is working, which is worth doing before you drive. If the pedal does not drop, the brake assistance may not be working and braking will need a lot of force. The Regulation on the technical conditions of vehicles requires the brakes to keep the required effectiveness, and the Road Traffic Act requires that the vehicle does not endanger safety.
Legal basis: Art. 66 para. 1 point 1 of the Road Traffic Act (Prawo o ruchu drogowym); § 15 para. 1 of the Regulation on the technical conditions of vehicles and the scope of their necessary equipment