1 - Vacuum hose
2 - Brake pipe
3 — Master brake cylinder
4 — Brake fluid reservoir
The driver's foot pressure on the brake pedal is amplified by the brake booster, using the vacuum created in the engine's intake manifold. In a diesel engine, the vacuum required for this purpose is created by a vacuum pump mounted on the engine flange. The operation of the brake booster should be checked if excessive force is required on the brake pedal to stop the vehicle.
1. Press the brake pedal at least five times with the vehicle not running. Then, with the pedal pressed, start the engine. The pedal should give noticeably under the driver's foot.
2. Otherwise, open the hood and remove the cover on the driver's side above the brake booster. The brake booster is located in the engine compartment directly on the bulkhead.
3. Disconnect the vacuum hose (1) at the brake booster. Start the engine. Place your finger on the end of the vacuum hose to check if there is vacuum.
Diesel Engine: Disconnect the vacuum hose from the vacuum pump and check the vacuum at the hose connection point.
Article borrowed from the web portal www.mercedesman.ru
4. If there is no vacuum, check the hose for leaks and damage, replace the hose if necessary.
5. If there is a vacuum, measure its value, replace the booster if necessary (work of the service station).