It is necessary to check the operation of the brake booster when the force on the brake pedal becomes unusually high.
With the engine off, press the brake pedal at least 5 times, and then, with the pedal depressed, start the engine. The pedal under the force of the foot should noticeably lower.
You can also disconnect the vacuum hose from the brake booster and start the car. Place your finger on the free end of the hose and check for vacuum (vacuum).
If there is no vacuum, check the vacuum hose for leaks and damage and replace if necessary. Tighten all clamps tightly.
Diesel engine: pull off the vacuum hose from the vacuum pump and check with a finger to see if there is a vacuum at the pump outlet. If there is a vacuum, then measure the vacuum value, if necessary, replace the brake booster in a workshop.