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Bryan Garner
02-07-2000, 12:10 AM
I have a 1989 750IL and either the brake booster or the Master Cylinder is leaking hydraulic fluid its been dripping from where the two components connect to each other. One guy that I talked to at bavarian Autosport said that it was probably a seal in the booster. Now I have the master cylinder and the booster off the car but looking at the booster the seal where the piston from the master cylinder goes into the booster looks fine. Could a seal inside the booster where I can't see it make it leak between the connection to the booster and the master cylinder? The only odd thing that I see is that their is a small opening in the bottom of the booster. Any Help would be great.

scott
02-07-2000, 02:28 PM
<i>: I just replaced my booster. It was leaking at the fitting at the base of the booster. The only suggestion I can give you is that if it is leaking green pentosin oil, it is the booster. If it is leaking brake fluid, its the master cylinder. I still have the old unit (booster) on my bench at home and I can take a look at it tonight if you want. I have a 91 750, but they should be the same. The Bentley manual showed an O-ring between the booster and master cylinder. Mine did not have it. It did not appear necessary as the unit units were individually sealed.<p></i>

Gilbert
02-08-2000, 10:33 AM
Mine has leaked sporadically out the hole in the bottom you mention, which I suspect is a vent hole. Mine is brake fluid, but its hard to tell unless the amount is significant.<br>Let us know what you find.<p><p><br><i>: I have a 1989 750IL and either the brake booster or the Master Cylinder is leaking hydraulic fluid its been dripping from where the two components connect to each other. One guy that I talked to at bavarian Autosport said that it was probably a seal in the booster. Now I have the master cylinder and the booster off the car but looking at the booster the seal where the piston from the master cylinder goes into the booster looks fine. Could a seal inside the booster where I can't see it make it leak between the connection to the booster and the master cylinder? The only odd thing that I see is that their is a small opening in the bottom of the booster. Any Help would be great. <p></i>

John
02-08-2000, 11:26 AM
Bryan,<p>Before you get to carried away, check the O-ring seal of the brake fluid reservoir (Plastic bowl). Mine started leaking and was all prepared to attack the master cylinder and/or booster. A 50 cent o-ring has delayed that project 3 years.<p>Trying to determine type of fluid? Mine was leaking brake fluid which peeled the paint from the boxed frame section down to shiny galvanized. I don't think the Pentosin will do this.<p><br>John 88 735iL (226K)<br>79 320i (250k)<br>95 Disco<p><br><i>: I have a 1989 750IL and either the brake booster or the Master Cylinder is leaking hydraulic fluid its been dripping from where the two components connect to each other. One guy that I talked to at bavarian Autosport said that it was probably a seal in the booster. Now I have the master cylinder and the booster off the car but looking at the booster the seal where the piston from the master cylinder goes into the booster looks fine. Could a seal inside the booster where I can't see it make it leak between the connection to the booster and the master cylinder? The only odd thing that I see is that their is a small opening in the bottom of the booster. Any Help would be great. <p></i>

Bryan Garner
02-08-2000, 11:56 PM
yea mine doesn't have an o-ring. I got a new booster from Bavarian Autosport and I now have to old one off. So this weekend we are going to put the new one on and see If it still leaks or not. one guy at Bavarian Autosport said that it is probably a seal in the booster that is leaking and that it was a common problem in my age 750.


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