I have a 1995 BMW 840ci with the 4.0 engine. I leaking hydraulic fluid from the part mounted to the fire wall. I'm lossing the S11 fluild and NOT brake fluid! I was told it was a brake slave value. The car has a Auto. Tranny. Would this be correct and if so where could I find/buy the part.


If this is not the part I need, what would you call it??

Grant

you are talking about the brake booster. Very EXPENSIVE if you buy it from GAULT. The actual repair (new O-Ring) costs $0.98 at NAPA, but will take you about an hour to do. I have done this repair with 100% success with the booster in the car. Some members have done it on the work bench, either way it is do-able with some DIY abilities.

have you checked the "easy" leak areas like the switches on the booster??

What TxGR8White said is right, it could be the 'O-Ring'.
The O-Ring gets hard over time. It is located on the booster side (right side) of the master cylinder/booster assembly. Just forward of the retaining screw is a square hole that allows the Pentosin to escape. This is the source of the spillage that you notice when the O-Ring starts to fail. If you put your finger under there, or look at it with an inspection mirror, you should feel or see the fluid at that spot.
I have a complete "right-up" and "how-to fix", I've saved. If you would like to see it give me an email as I'm not alowed to 'paste' here.....I guess because I'm to new to this site.
Hope this helps,
P. Ford