A QUESTION ABOUT BRAKE SYSTEM. (servo)?

Most vehicles use hydraulics to apply pressure to brake drums/discs via pads/shoes, i think your confusing the ABS which regulates pressure/contact over time/duration. If your engine stalls, you'll still have brakes.

I think Ralph is right you are confusing the brake system with the ABS system. Your brakes are worked by a vacuum booster, if the engine would shut down there would still be enough vacuum in the booster to stop the car with the same power as it would if the engine was running. The only problem there is that you would loose the boost every time you pumped the brakes and then it would become very hard to stop but the brakes would still work. Read up on the ABS system on the net and I think you will find that is where there are servo motors and even then if the engine shut off the servo is electric and would still work. I love your last line- you can't because it is dangerous? Do you want to find out what happens by accident? Got a parking lot in your neighborhood?

I think the mad Thumbs-Downer hit thebax. He is exactly correct - without power boost the pedal becomes quite hard and the brakes become less effective, usually to the point that it is not humanly possible to lock the brakes on dry pavement. Servo systems (like the brake booster, as we call it in the US) are self-regulating power assist systems. Power steering is another example - a sensor in the steering column or rack controls the power assist. There are three types of servo assist (power boost) in cars and trucks today. Almost all gasoline powered vehicles with conventional power trains use manifold vacuum from the engine. In those systems the vacuum is stored so there are a couple good stops left after the engine stops. In hybrid vehicles and electric cars the engine does not always run so air pumps are typically used to operate the servo. In that case it makes no difference at all whether the engine is running... it is just another day. Diesel cars often use an engine driven vacuum pump, which behaves like gasoline engines in this sense. Diesel trucks may have hydraulic pumps, so boost quits immediately if the engine (or pump) quits. In my F350SD diesel work truck the same pump provides servo assist to the steering and brakes, as I learned to my dismay on a mountain road when the pump bypass jammed open and killed the assist to both systems instantly.