Raise and support the car.
Clean the brake lines with a degreaser.
Caution: The tubes are coated with a plastic covering to prevent corrosion. If the covering is damaged, the tubes will begin to rust, so they should not be cleaned with a wire brush, fiberglass or sharp objects.
Inspect the lines that go from the master cylinder to each wheel cylinder. The master cylinder is located in the engine compartment under the brake fluid reservoir.
Brake pipes must not be twisted or compressed. If there is the slightest trace of rust or abrasion, the pipes must be replaced. Brake hoses connect the pipes to the wheel cylinders in places where the moving parts of the car are located. They are made of a material resistant to high pressure, which, however, over time can become porous, deform or get damaged. In this case, the hoses must be replaced immediately.
In order to localize the damage, you can try to bend the brake hose in one direction and then the other. When replacing hoses, follow their color markings.
Turn the steering wheel all the way to the right and left. The brake hoses should not touch any moving parts of the car.
Check for traces of moisture at the connection points of the brake pipes and hoses.
Note: If there are traces of brake fluid on the reservoir, this does not necessarily indicate a faulty master cylinder. Brake fluid may be leaking through the vent hole in the reservoir cap or through the cap seal.
Article obtained from this portal: mercedesman.ru