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Re: Brake Fluid Leak (archive)

[ Follow Ups ] [ 5-series (E34) Message Board ] [ Msg. Board FAQ ]

Posted by moots on November 23, 2000 at 06:17:40:

In Reply to: Brake Fluid Leak posted by Gary M on November 22, 2000 at 22:16:22:

I have not experienced this leak on the Bimmer but have gone thru this on my previous Japanese cars and the basics are the same.The fault lies on the piston O ring(4 pieces normally,with 2 of them on 1 piston)inside the brake master cylinder.If you're fortunate,only the O rings need to be replaced.Otherwise if the cylinder inner surface is scored,then the master cylinder itself requires replacement.The purpose of the gasket between master cylinder and booster is not to contain the fluid but merely acts as a seal between the two components.
To me this is a DIY job but can get pretty messy and bleeding should not pose a big problem if procedures are followed.It would help if you are mechanically inclined.

moots '90 520i


Has anyone had this problem and what was your solution? I've got a brake fluid leak behind the master brake cylinder going into the brake booster pump. Is this a failure of a gasket or an O-ring between these two items or is it something else? Is it a self service fix or do I need to bring it to a mechanic? My main concern is the bleeding of the brake system and the risk of getting a lot of air into the system.





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