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 Post subject: Master Cylinder Vent
PostPosted: Wed Apr 15, 2015 9:24 pm 
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Location: Elizabethton Tn
I noticed there was mud under the rubber next to the lid in my brake reservoir. If the brake fluid is kept FULL, do I need that little vent hole In my lid? I assume that vent allows the rubber diaphragm to be pulled down as the fluid level drops. Which is to keep the fluid from sloshing around and sucking air into the piston????

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 Post subject: Re: Master Cylinder Vent
PostPosted: Thu Apr 16, 2015 12:11 am 
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I have pondered this a few times as well.. :roll: :roll:

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 Post subject: Re: Master Cylinder Vent
PostPosted: Thu Apr 16, 2015 6:37 am 
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Location: Pittsburgh,Pa.
Unless the contamination is getting into the fluid itself,
why not add a barbed fitting where the vent hole is?
The smaller Humphrey barbed air fittings have straight threads
...and a nut can secure the fitting to the thin-walled cap.
A bulkhead style fitting is better, especially if it has rubber
sealing. Add a rubber hose vent line and run it way high
up on your frame. A one way check valve will be needed
at the hose end.

The muddy water can still get up around the cap threads
(if that is the style reservoir that you have). Your only
other choice is an original remote car style reservoir.


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 Post subject: Re: Master Cylinder Vent
PostPosted: Thu Apr 16, 2015 1:39 pm 
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Location: Elizabethton Tn
Here is what i have after power bleeding, which is awesome. I could attach a hose to the valve stem and run the vent else where. But I believe I will run it for awhile sealed and see what happens. Any other opinions?

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 Post subject: Re: Master Cylinder Vent
PostPosted: Thu Apr 16, 2015 2:05 pm 
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JMO- the cover has to be free vented. If you let air in and not out it will hold pressure when you release the pedal. The hose sounds like a good idea but I would just loop it over with the open end facing down but above the level you ever expect to be in water


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 Post subject: Re: Master Cylinder Vent
PostPosted: Thu Apr 16, 2015 3:52 pm 
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Location: Elizabethton Tn
Oops forgot my photo. That makes sense Herbie.Image

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 Post subject: Re: Master Cylinder Vent
PostPosted: Fri Apr 17, 2015 10:01 am 
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Location: Pittsburgh,Pa.
For what its worth, I have never been much of a fan
of anything other than dual master cylinders with
a reservoir that is mounted up high. Anything else
seems to be obsolete or great for a show buggy.
My single cylinder has been a curse to me. I went
all of the way to the bottom of a mountain trail
with no brakes one weekend. It scared the God-fearin'
life out of me.


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 Post subject: Re: Master Cylinder Vent
PostPosted: Fri Apr 17, 2015 11:44 am 
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Location: Elizabethton Tn
I've never had anything but the original bus master cylinder since my first buggy in 1986. Never had any problems, knock on wood...lol

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 Post subject: Re: Master Cylinder Vent
PostPosted: Fri Apr 17, 2015 1:07 pm 
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Hey jimp, are you running 4 wheel brakes or two?

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 Post subject: Re: Master Cylinder Vent
PostPosted: Fri Apr 17, 2015 1:59 pm 
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Location: Pittsburgh,Pa.
bigDsmith wrote:
Hey jimp, are you running 4 wheel brakes or two?


I only run rear brakes. Backing down hills with 4 wheel brakes
takes away the ability to steer.


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 Post subject: Re: Master Cylinder Vent
PostPosted: Fri Apr 17, 2015 7:01 pm 
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So you run a dual master cylinder.....one going to one wheel and the other to the other wheel. Hmm...so if you loose one line you Still have brakes on the other wheel?

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 Post subject: Re: Master Cylinder Vent
PostPosted: Sat Apr 18, 2015 6:36 am 
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Location: Pittsburgh,Pa.
bigDsmith wrote:
So you run a dual master cylinder.....one going to one wheel and the other to the other wheel. Hmm...so if you loose one line you Still have brakes on the other wheel?


That would be different!
Actually, here is a diagram of my redundant system:
http://www.realoem.com/bmw/diagrams/p/k/4.png

Many stock 4 piston front calipers have dual circuits.
Many aftermarket retrofits (ex. Ford Mustang) too.


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 Post subject: Re: Master Cylinder Vent
PostPosted: Sat Apr 18, 2015 10:14 am 
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Ok. cool.

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