[AJD] What are failed Master Brake Cylinder Symptoms?

[Bruce Mahr]

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
>
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>
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