I didn't read enough into it, but I wonder if the silicon-based brake
fluids draw less water.  They are incompatible with the glycol-based
ones, but I suppose if you fully flushed the system it would be usable
even in the venerable vanagon?

On 6/29/16, Dennis Haynes <d23haynes57@hotmail.com> wrote:
> Brake fluid (glycol) is used as it gets along well with certain
> rubber/plastic parts. Yes it can absorb moisture especially since most of
> the system is exposed to ambient temperature changes and it not heated
> except at the calipers or pistons to drive the moisture out. Worse is that
> our vans have open caps to let air in as the fluid expands and contracts.
> Year ago many vehicles had a master cylinder with a cover and bladder over
> the fluid. As the fluid level went down the bladder would pull down with so
> fresh air never entered those systems.
>
> In reality bakes should be inspected at some regular basis, at least once
> year or after any unusual situation such as an emergency stops or long term
> storage. At that point it is not a big deal to flush through some of the
> fluid. Same for power steering fluid. Some of that darkness could be from
> the rubber hoses or just from the moisture making the fluid cloudy. Changing
> it every two or three years will make most issues go away. Still, even with
> fresh fluid overheating the brakes to the point that the fluid gets to the
> vapor point will cause a low pedal next application. At that point there can
> also be caliper or cylinder damage so simply bleeding the brakes may not be
> sufficient.
>
> Dennis
>
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> C. Abney
> Sent: Wednesday, June 29, 2016 7:21 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Sticky brakes
>
> The properties of brake fluid make it a frequent topic of discussion, and
> you know it makes me wonder just how much or little thought has been put
> into its continued use.
>
> Brake fluid absorbs water from the environment.  This water then causes
> corrosion in the system, brake fade when the brakes get hot, it might
> increase dissolved gases in the fluid.
>
> I've never seen old brake fluid bled out that wasn't filthy.  Where's that
> from?
>
> What is it about brake fluid that makes it indispensable to a braking
> system?  Isn't just about a certain level of viscosity?  If that's so can't
> something better be substituted for it?
>
> That said, there is a wide variation in the wet/dry boiling points of brake
> fluid.  Even within one DOT rating.  The vanagon uses dot 4, but dot 5.1 can
> also be used and is compatible with dot 4, and has a wet boiling pt. MINIMUM
> of 180C.
>
> For some reason the high boiling point stuff, even though it's the same
> chemistry as dot 4 in general, is much more expensive.  You're better off
> being diligent about changing your brake fluid regularly.
>
>
>
>
> --
> There's no .sig like the present
>

--
There's no .sig like the present