Raise and support the car.
Clean the brake lines with a degreaser.
Attention: To prevent corrosion of the tubes, they are covered with a plastic coating. If the coating is damaged, the tubes will begin to rust, so they should not be cleaned with a wire brush. fiberglass or sharp objects.
Inspect the tubes going from the master cylinder to each wheel cylinder. The master brake cylinder is located in the engine compartment under the brake fluid reservoir.
Brake pipes must not be twisted or compressed. At the slightest trace of rust or abrasion, the tubes must be replaced. Brake hoses connect tubes to the wheel cylinders where the vehicle's moving parts are located. They are made of high-pressure-resistant material, which, however, can become porous, warp or be damaged over time. 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 the other. When replacing hoses, follow their color marking.
Turn the steering wheel all the way to the right and left. In this case, the brake hoses must 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 malfunction of the master cylinder. Brake fluid may leak through the vent in the reservoir cap or through the cap seal.