TheSamba.com :: View topic - That little hole in the brake master cylinder

Fri Feb 26, 2010 11:30 pm

A minuscule amount of brake fluid is coming out of mine. I replaced the last one two months ago because of the same thing. What gives?

Of course, it shouldn't leak at all - so why did they put that little hole there?

Jason

Sat Feb 27, 2010 12:28 am

jrehm wrote: A minuscule amount of brake fluid is coming out of mine. I replaced the last one two months ago because of the same thing. What gives?

Of course, it shouldn't leak at all - so why did they put that little hole there?

Jason

They wanted any master cylinder to leak (weep) outside of the brake booster area which is under vacuum and can fill up with brake fluid, a very ugly thing to do to your booster.
Colin

Sat Feb 27, 2010 1:03 am

our replacement ATE leaked out the weep hole the first pump only. I believe it was fluid used to build it. Do you actually have a leak or could you be seeing that first drop of fluid still?

If your last one went bad it could have filled the booster with fluid and you could be seeing fluid from there. Did you try to get any fluid from the booster after the last master leaked?

Last, the reason masters and slaves go bad is usually rust. That comes from water being pulled into the brake fluid from the air. Brake fluid should be changed once a year.

Sun Mar 07, 2010 6:59 pm

no rust on either. Both lasted less than 6 months and were ATE from Bus Depot. Is there anything else that could cause these to go? Does the rod that connects to it need adjustment for each master?

Jason

Sun Mar 07, 2010 8:03 pm

Jason - did you change all the fluid when you replaced it? What kind of fluid?

How often do you adjust your rear brakes? If they get loose it will allow the pistons to travel farther which can aggravate the situation.

As I said, ours leaked assembly fluid the first few times we pumped. It has been dry since.

Some brakes require adjusting the pushrod but that wouldn't cause the issue you have. You either have fluid leaking past the seals internally (defective), fluid dripping down that is fooling you into thinking it is coming from the weep hole or fluid in the booster draining out the weep hole.