[AJD] What are failed Master Brake Cylinder Symptoms?

Ed Allandar eallandar at rohrerbus.com
Thu Jul 14 05:20:36 PDT 2005


Dean-
Sounds to me like you have 2 problems. 1. Being the master cylinder 2. Being
the vacuum booster or hydro-vac. The Pedal fad sounds like fluid passing by
the rings and cups on the master cylinder piston and should be rebuilt. The
unexplained fluid loose tells me the booster is bad and the brake fluid is
being sucked back into the engine intake by engine vacuum. Some boosters my
be rebuilt but I would recommend buying a remanufactured unit. The master
cylinder you should have no problem rebuilding yourself. Good luck

Ed Allandar
Rohrer Bus Service
P.O. Box 100 - 1515 State Road
Duncannon, PA 17020-0100
717.957.5114 Direct
717.418.4401 Cell
1-800-735-6700 x223 Toll free
717.957.4884 (fax)
eallandar at rohrerbus.com

-----Original Message-----
From: antique-johndeere-bounces at lists.antique-tractor.com
[mailto:antique-johndeere-bounces at lists.antique-tractor.com]On Behalf Of
Dean VP
Sent: Thursday, July 14, 2005 2:22 AM
To: 'Antique John Deere mailing list'
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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