Leaking brake master cylinder

    Dear friends.

    I´m changing the old brake master cylinder on my w111 230s for a new ATE (A0014306301) master cylinder. As you know there´s a small tiny hole near the rim under the cylinder body. After install the cylinder and start bleed it I notice there´s some fluid coming out of the hole.......Every stroke on the brake I can see more fluid coming out.

    Can you help me to fix this problem.

    ...the master cylinder is leaking inside, the little hole prevents the the brake booster from getting flooded with brake fluid !


    Give it back to the dealer and demand another one !

    hello bigbellysurfer ,


    in appointment to your describtion , it seems to me, that the new master-cylinder does not work correctly. There must not be any leak at that hole . Maybee the last rubber sealing of the piston is damaged or maybee there are scratches or rust in the surface of the cylinder .

    You will have to order a new mastercylinder once again.


    best regards , Ralf

    Quote from Obelix

    ...the master cylinder is leaking inside, the little hole prevents the the brake booster from getting flooded with brake fluid !


    Give it back to the dealer and demand another one !

    Whta´s really strange I just istall a new one, not rebuild but I understand, now, the reason for the hole.

    thank´s for your help

    Yes, going to send this one back. Thanks a lot