As your brake friction parts wear down you'll get slightly increasing
travel of the wheel cylinder pushers.....this results in an
ever-increasing (albeit slight) increase in the required volume of the
sytem. So you can get falloff of the level without having a leak, but
it shouldn't be very much.
Out of laziness I've always kept unused brake fluid around in
partially filled bottles, but now this thread has got me
thinking.....how much water can be introduced into the part-used
bottle? It's the same deal as a partly-filled gas tank, when water
condenses out of the air in the tank. A full bottle has little air at
the top, so it will be better than a bottle with more air at the top.
If I become incredibly bored tomorrow I guess I'll do the calculations
to see how much water you might expect to introduce into the bottle of
fluid if you leave it only partially full. This will vary of course
with the humidity of the air at the time you trap it in the bottle.
Assuming I get that far, someone will have to tell me if that amount
of water makes any difference......
On a separate but equally bothersome note, we seem to be dancing
around the issue of whether brake fluid has a shelf life (apart from
whether it has been contaminated with water). Does anyone know?
Anyone actually have a copy of the DOT 3 & 4 specs? Does US DOT 3
really eat rubber?? Man, I never thought any of this would bother me
but now it officially does!!!
MD
---Jackson Zimmermann <JZIMMERM@exch.co.albemarle.va.us> wrote:
>
> I would question why you would ever need to top the brake system up.
> There should be no leakage of any sort, I for one would blanch at
> driving any car that needed occasional brake fluid (I remember my 1970
> Toyota HiLux Pickup and its regular master cylinder failures all too
> well). Typically opened brake fluid is kept around for long periods
of
> time and mixed with new brake fluid, degrading the value of new
fluid...
>
>
> True that brake fluid in a tightly sealed can may be better than
that in
> the system, but it is not nearly as good as that from a new sealed
can.
> Moisture is death to brake systems.
>
> -----Original Message-----
> From: Trevor Boicey [mailto:tboicey@brit.ca]
> Sent: Thursday, October 15, 1998 2:35 PM
> To: Jackson Zimmermann
> Cc: spridgets@autox.team.net
> Subject: Re: Leaf Springs & Brake Fluid
>
>
> Jackson Zimmermann wrote:
> > Also never reuse brake fluid from an open
> > can (even the LMA), always chuck it after you've used as much as you
> > need as brake fluid starts absorbing water from the moment it is
> opened.
>
> This is something I question a bit.
>
> If I have an empty system and a full bottle, then open
> the bottle and fill the system, the two "systems" would
> start acucmulating water at the same time.
>
> Since the bottle seals and the system as a breather, I
> would surmise that the bottle would actually do slightly better
> at keeping the water out.
>
> If nothing else, topping up the system with the fluid
> from the bottle should not INCREASE the percent water
> content.
>
> If month old fluid on the shelf is garbage, I am not sure
> how that prevents month old fluid in the SYSTEM from being
> garbage as well.
>
> --
> Trevor Boicey, P. Eng.
> Ottawa, Canada, tboicey@brit.ca
> ICQ #17432933 http://www.brit.ca/~tboicey/
>
|