[AT] RE: What are failed Master Brake Cylinder Symptoms?

[Andy Glines]

Dean, you have gotten some good ideas from the list.  I Don't remember you 
telling us where the fluid went.  Did you find where it lealed out?  Is 
yours one with the booster mounted on the firewall of the truck or does it 
have the hydrovac unit under the floor?  Have you looked at the back side of 
each wheel to look for leaks at the wheel cylinders?  When you refilled the 
MC and drove it how did it do?  I've had two MC fail on me the first one 
allowed the pedal to go to the floor with no brakes.  I could pull the pedal 
back up with my foot and might have brakes on the next try.  Probably a bad 
check valve (1976 3/4 chevy).  On my 1973 Loadstar 1700 the pedal would 
travel down but not return.  I found that the rubber piece on the piston had 
swollen and was sticking in the bore.  I suspect that someone put oil in the 
MC instead of brake fluid.  I will rebuild the entire brake system on this 
truck before putting it on the road.
>----- 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 10:06 PM
>Subject: [AT] 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