Date:         Thu, 1 May 2014 10:45:17 -0700
Reply-To:     Don Hanson <dhanson928@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Don Hanson <dhanson928@GMAIL.COM>
Subject:      Re: Brakes- the saga continues
In-Reply-To:  <9A0CD4EF-9E41-4F62-B151-A5E60D7FC4AA@shaw.ca>
Content-Type: text/plain; charset=UTF-8

  OK a trick I learned at the racetrack....Use different colors of fluid
when you bleed the brakes to be assured you've purged all the old dirty
contaminated fluid....I use ATE Super Blue and ATE (the normal gold colored
stuff) , alternating each time I change the brake fluids.....

  When you see the other color coming out of the bleed tube you can be
assured you have completely done the job.....but....if you are sloppy with
any part of the job air can sneak into the lines behind the new fluid and
you will again have 'soft pedal'.....

 I musta bled my brakes a few thousand times when I raced my Porsche
because when racing,  your brakes will get you more 'passes' than hundreds
of horsepower....and ever the Big Red Brembo super effective hollow
perforated disc brakes on the Porsche were not immune to boiling the brake
fluid etc...


On Thu, May 1, 2014 at 8:01 AM, Alistair Bell <albell@shaw.ca> wrote:

> I can't comment on compressibility of fluid with large bubbles versus
> micro bubbles of air, but I do know that brake fluid does , or can, have
> air dissolved in it.
> Not to be confused with bubbles, which is entrapped air.
>
> Alistair
>
> > On May 1, 2014, at 7:23 AM, Gnarlodious <gnarlodious@GMAIL.COM> wrote:
> >
> > One big advantage of the vacuum method is that microscopic bubbles
> > expand under vacuum, causing them to flocculate faster and rise to the
> > top sooner. I've noticed with pressure bleeding it can take some time
> > to get microscopic air out of the system. If you watch fluid through a
> > clear tube you see cloudy brake fluid coming out under pressure, but
> > that just means microscopic air bubbles are incorporated in the fluid.
> >
> > As a wild guess, I would say that one large bubble has more
> > compressibility than a million small bubbles totaling the same volume
> > of air. That would explain why your Vanagon's brakes feel fine
> > immediately after bleeding but a few days later they are all squishy.
> > This has happened to me several times and is something of a mystery.
> > Someone more versed in physics could dig up the facts, I nominate
> > Alistair Bell.
> >
> > -- Gnarlie
> >
> >
> >
> >> On Thu, May 1, 2014 at 7:38 AM, Mike B <mbucchino@charter.net> wrote:
> >> Regarding the brake bleeding process. It all depends on you method used.
> >>   If you use a Motive pressure bleeder, it's a simple one-man process,
> >> and it's hard to "do it wrong".
> >>   If you use a vacuum hand-held, hand operated brake suction device,
> >> you need to grease the threads of each bleeder to prevent suction of air
> >> through the threads, but otherwise, it's also pretty hard to "do it
> wrong".
> >>   If you do it the old-fashioned 2-man way, there's a way to do it
> >> wrong and a way to do it right.  The right way to do it is to attach an
> >> 18" rubber hose to the bleeder and put it in a small plastic or glass
> >> jar with a inch or so of brake fluid in it. (you could also buy a '1-man
> >> brake bleeder' tool, which is basically this).  One guy does the pump
> >> and hold on the pedal, while the other guy opens the bleeder and watches
> >> the fluid/ air squirting into the jar.  Repeat on each wheel until
> >> there's no more bubbles, being sure to stop every so often to check that
> >> the reservoir isn't getting too low.  Use 3 sharp quick pedal strokes to
> >> force air from all of it's hiding places, then hold until instructed to
> >> let go by the guy manning the bleeders.  Start at the farthest away
> >> (right rear), then move to the next farthest bleeder (left rear), then
> >> right front, then left front.  You may need to go around them two or
> >> three times to get it all, and a hard pedal with no squishiness is an
> >> indicator that you're done. Be sure to do enough to clean all of the old
> >> dark fluid out and replace it with fresh clear fluid.
> >>  If you do it without the jar and hose, you will make a mess of
> >> spilled fluid everywhere (it eats paint!), have lots of problems (like
> >> Don mentions) and depending on your methods and procedures, you may not
> >> be able to get every last bubble of air out of the system.
> >>
> >> Mike B.
> >>
> >>
> >>> On 5/1/2014 9:17 AM, Don Hanson wrote:
> >>>
> >>>   Squshy brakes:   Bleeding the system carefully should stop that.
> >>> "Carefully" being the operative word...Brake bleeding is intolerant of
> >>> sloppy or slipshod work....any lapse at all during the brake bleeding
> >>> process can render the whole procedure a waste of time...It can be a
> >>> tedious job, relatively simple in concept but one that demands you
> make no
> >>> mistakes along the way...It takes a fraction of a second of
> inattention to
> >>> allow a bit of air to enter the hydraulics...a very very small bubble
> of
> >>> air anywhere in the system will cause the spongy brake pedal feel..
> >>>
> >>>    Another symptom you may be encountering here is warped rotors,
> >>> oscillating as the wheel turns, a wobble that pushs the brake pistons
> way
> >>> back into calipers.   So rather than an actual 'soft pedal' from air in
> >>> the
> >>> system, you may be needing to give the brakes a few pumps to move that
> >>> brake pad back to where it will actually grip the warped rotor...
>