Here's my opinion: "Better safe than sorry"
This leads to the following personal rules:
1) Use DOT 4 fluid (or DOT 5 under certain conditions), since SOME DOT 3
formulations eat natural rubber seals. (Do you know what kind of seals are
in your brakes? What formulations different manufacturers use? I don't.)
2) Buy DOT 4 brake fluid in small bottles, and use a fresh bottle whenever
possible.
Following these rules, I spend a few $$$ more on brake fluid, but a whole
lot less on body repair (the car's and my own).
Chris Kotting
ckotting@iwaynet.net
On Thursday, October 15, 1998 6:27 PM, Michael Dietsche
[SMTP:mdietsche@yahoo.com] wrote:
>
> 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/
> >
>
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