Date:         Sat, 14 May 2016 05:27:40 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Home Made Brake Pressure Bleeder: *might* add moisture to
              brake fluid?
Comments: To: Neil N <musomuso@GMAIL.COM>
In-Reply-To:  <CAB2Rwfj9SQ0s3eeFrmTXCJyq_EdycAmv-d=Q+fCXFB7PrPf=qQ@mail.g
              mail.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 05:27 PM 5/13/2016, Neil N wrote:
>I know that's a far fetched idea, and I think the answer is "no" but.....

Not far-fetched at all.


>When using a home made pressure bleeder to pressurize the brake fluid
>reservoir with AIR
>when bleeding the brakes, would this air add moisture to the brake fluid?

That would depend how much moisture is in the air, wouldn't it?  The
higher the humidity the more water the fluid will absorb.  The fluid
is hygroscopic (possibly the new synthetic ones aren't) so it will
actively pull moisture from the air (just as salt will do at high
humidities) but it's not an instant process.  Speed depends on how
much surface is exposed to air as well as the concentration of water
vapor and the pressure.

You can reduce surface area by floating a barrier in the reservoir,
and reduce humidity by passing the air through a bed of silica gel,
or by freezing or condensing it out.  My hunch is a few minutes
exposure at ordinary humidities won't make a practical difference,
but there's a reason why you keep the brake fluid bottle closed and
preferably squeeze it first so there's minimum headspace.

Yrs,
d