[AJD] What are failed Master Brake Cylinder Symptoms?

[Bus Driver]

Fluid going around the piston inside the MC is not unusual. We call it
internal bypass. Rebuilding is not difficult, but I have had better service
life from the rebuilds bought at the parts store than from my own rebuilds.
> ----- Original Message ----- 
> From: "Dean VP" <deanvp at att.net>
> To: "'Antique John Deere mailing list'"
> <antique-johndeere at lists.antique-tractor.com>
> Sent: Thursday, July 14, 2005 1:21 AM
> Subject: RE: [AJD] What are failed Master Brake Cylinder Symptoms?
>
>
> > Bruce:
> >
> > Let me try to establish the sequence again.
> >
> > 1.) Truck sets unused and outside over winter. Very wet but not much
> > freezing weather.
> > 2.) Spring check - When pressing break pedal no pressure. Peddle to the
> > floor.
> > 3.) Try to remove filler cap on Master Cylinder - Top (hex head) breaks
> > off
> > w/o getting cap off. Finally get cap off w some difficulty. MC fluid
> > cavity
> > dry as a cork. Fill with HD brake fluid.
> > 4.) Try pumping brake. No pressure. Pump and pump and pump, an
> > extraordinary
> > # of times. Almost give up but eventually get some pressure. But bleeds
> > down
> > with constant pressure. If not pressed for a few minutes needs to be
> > pumped
> > several times to get pressure back and then still bleeds down. Feels
like
> > fluid being pumped out a leak somewhere but no visible leak and fluid
> > level
> > in MC not going down. Am getting some splash back in the MC cavity since
> > no
> > cap on at present.  Occasionally will give impression it will hold under
> > pressure but then if left alone for awhile and then pumped up again it
> > will
> > bleed down.
> > 5.) Not spongy like an air bubble at all. When peddle pressed and bleeds
> > down it actually feels like a fluid leak but not losing fluid and no
fluid
> > leaks visible. Doesn't feel like air in the lines. Feels just like when
> > one
> > opens the brake lines when bleeding them.
> > 6.) Not getting any real pressure to the wheel brakes. Very scary and
> > dangerous.
> >
> > Does this help in isolating the problem more?
> >
> > I guess I will try replacing the MC in the morning. But my gut tells me
> > there is something more wrong besides the MC. Maybe I'm fencing with
> > windmills. I have had all the wheel brake cylinders replaced a couple of
> > years ago and all brake parts and adjusters cleaned up and lubed in the
> > wheel hubs. But the MC was not replaced that I am aware of. I recall, at
> > the
> > time, finding that a bit unusual since all the wheel cylinders were
> > replaced. Just don't trust this sucker right now at all.
> >
> > I don't recall ever having a MC fail before so maybe I'm experiencing a
> > new
> > phenomenon. I've had one really serious incident with this truck before
> > due
> > to the brakes and brake lines. This makes me really nervous. Damned
scared
> > in fact. I dodged a bullet one time, and don't think I'll get a second
> > chance.
> >
> > How does a Master Cylinder lose fluid w/o showing any visible signs?
Don't
> > understand that at all. Ends up in Vacuum assist? Leaking wheel
cylinder?
> > Behind firewall? Really confused!
> >
> > Dean A. Van Peursem
> > Snohomish, WA 98290
> >
> > I'm a walking storeroom of facts..... I've just lost the key to the
> > storeroom door
> >
> >
> > www.deerelegacy.com
> >
> > http://members.cox.net/classicweb/email.htm
> >
> >
> >
> > -----Original Message-----
> > From: antique-johndeere-bounces at lists.antique-tractor.com
> > [mailto:antique-johndeere-bounces at lists.antique-tractor.com] On Behalf
Of
> > Bruce Mahr
> > Sent: Wednesday, July 13, 2005 8:53 PM
> > To: Antique John Deere mailing list
> > Subject: Re: [AJD] What are failed Master Brake Cylinder Symptoms?
> >
> > Dean: Were the brakes OK after filling the master cylinder with fluid?
If
> > they were then you need to rebuild or replace the master cylinder.
> > If the problem showed up after filling the master cylinder, then you
need
> > to
> >
> > bleed the entire system, because air in it is causing your problem.
> > Air in the lines and bad seals in the master cylinder will both give you
> > the
> >
> > problem you have, so it depends on when it showed up which you should do
> > first.
> > Wheel cylinders can leak enough from setting to empty the master
cylinder
> > without any visible evidence at any of the wheels for quite a long time,
> > due
> >
> > to brake dust and dirt inside soaking up the fluid before it becomes
> > visible
> >
> > on the outside.
> > Also the vacuum booster cylinder can leak into the vacuum chamber and
will
> > drain the master cylinder but not show up externally.
> > Your problem is definitely air, but why depends on too many things. I
> > would
> > try bleeding the system first.
> > I deal with this on my customers farm trucks all the time because of
> > setting
> >
> > most of the year.
> >
> > Bruce Mahr
> >
> > ----- Original Message ----- 
> > From: "Dean VP" <deanvp at att.net>
> > To: <at at lists.antique-tractor.com>; "AT JD"
> > <antique-johndeere at lists.antique-tractor.com>
> > Sent: Wednesday, July 13, 2005 9:06 PM
> > Subject: [AJD] What are failed Master Brake Cylinder Symptoms?
> >
> >
> >>I have a brake problem all of a sudden on 68 Ford N600. Brake pedal took
> >> several pumps to develop pressure, then bleeds off under pressure. If
not
> >> used for e few minutes takes several pumps again to get pressure and
then
> >> bleeds down slowly under peddle pressure.   No improvement over time.
> >> Can't
> >> tell if all four wheels are getting brake activity but there isn't much
> >> braking power at all even under heavy foot peddle pressure. Fluid level
> >> ok
> >> and not dropping. Something is terribly amiss but I don't know how to
> >> isolate the problem?  Master Brake Cylinder? Vacuum assist leaking? All
> >> four
> >> hub cylinders leaking? Leaking line? (No loss of fluid right now but
> >> Master
> >> Cylinder went dry over the winter during non-use!) A bunch of air in
the
> >> lines?
> >>
> >> I don't recall having brakes fail this drastically before or not
> >> eventually
> >> self bleed. I'm really confused. Where do I start to diagnose the
> >> problem?
> >> Can this just be a Master Cylinder failure or is it something else?
Sure
> >> not
> >> safe to drive this way.
> >>
> >> I'm reluctant to start throwing parts at the problem until I know for
> >> sure
> >> what is wrong. Not sure I've ever had this major of brake failure
before.
> >> I
> >> need help.
> >>
> >> Dean A. Van Peursem
> >> Snohomish, WA 98290
> >>
> >> I'm a walking storeroom of facts..... I've just lost the key to the
> >> storeroom door
> >>
> >>
> >> www.deerelegacy.com
> >>
> >> http://members.cox.net/classicweb/email.htm
> >>
> >>
> >>
> >>
> >>
> >>
> >> _______________________________________________
> >> Antique-johndeere mailing list
> >> http://www.antique-tractor.com/mailman/listinfo/antique-johndeere
> >>
> >
> >
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>
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