Warning: Brake fluid is poisonous, so be careful not to let it come into contact with your body or your vehicle's paintwork.
Check that the brake fluid level in the transparent reservoir is between the MIN and MAX marks.
First, wipe the area around the filler cap and unscrew the cap from the brake fluid reservoir.
Add brake fluid up to the MAX mark on the reservoir. Use only the specified brake fluid, as mixing brake fluids is not allowed.
Check the operation of the brake fluid level indicator lamp. Turn on the ignition and press the button on the top of the brake fluid reservoir. The indicator lamp should light.
(Original material on the website mercedesman.ru)