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Re: [Healeys] troubleshooting rebuilt Girling BJ8 brake servo

To: "R. Cobb" <rcobb@earthlink.net>
Subject: Re: [Healeys] troubleshooting rebuilt Girling BJ8 brake servo
From: Michael Salter <michaelsalter@gmail.com>
Date: Wed, 21 Oct 2015 16:39:29 -0400
Cc: "healeys@autox.team.net" <healeys@autox.team.net>
Delivered-to: mharc@autox.team.net
Delivered-to: healeys@autox.team.net
References: <5626BF10.1090302@earthlink.net>
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Hi Bob,
In my experience the Girling servo units can be very difficult to rebuild
satisfactorily.
The symptoms that you describe are however more indicative of air in the
system than those typical of servo difficulties.
If the servo is not working properly the typical symptoms are no servo
action at all or brakes dragging and/or locking on.
To check the servo action pump the brake pedal several times with the
engine not running then,  with pressure on the brake pedal, start the
engine and the pedal should drop a little as manifold vacuum is
established. If the pedal drops the servo is working.
The other problem is evident when you drive the car.. First the brake pedal
will become quite "hard" and there will be no "free play" at the top of its
stroke next the brakes will get very hot and eventually the car will stop
moving because the brakes are locked on..
The usual cause of that problem is the failure of the large piston within
the servo unit to return fully to its rest position when the brakes are
released. That is where the "thinner sponge" thing comes in. The correct
solution is to have the inside of the servo "chest" re-coated with a
special slippery coating. There should be more information on that way back
in the archives.
Hope that helps,

Michael S
BN1 #174
(4 wheel drum brakes ..no servo)



On Tue, Oct 20, 2015 at 6:24 PM, R. Cobb <rcobb@earthlink.net> wrote:

> Unit was rebuilt using kit from Moss.
>
> Symptoms, following bleeding hydraulic brake system (no differences noted
> whether car running or not): On first try of brakes, nearly no braking,
> with pedal going almost to floor.
>
> Second try, sometimes a release is felt in the pedal (with an associated,
> slight "pop" sound) with a bit more braking and less travel of pedal.  By
> the third try, the pedal travel seems more normal, and the braking is
> improved, though not up to the level expected.
>
> The above pattern has been replicated numerous times, with the thinking
> that perhaps if something were binding, it would work-in. No such luck.
>
> Any thoughts?
>
> I recall that some months ago a contributor mentioned having had to
> install a thinner sponge rubber ring for under the piston seal...because of
> binding(?).  Could this be the issue?  Would this result in the behavior
> I'm experiencing?
>
> Thanks in advance.
>
> Bob
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>
>


-- 
*If you can't fix it with a hammer, you've got an electrical problem.*

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Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div class=3D"gmail_default" style=3D"font-family:comic sa=
ns ms,sans-serif;font-size:small">Hi Bob,<br></div><div class=3D"gmail_defa=
ult" style=3D"font-family:comic sans ms,sans-serif;font-size:small">In my e=
xperience the Girling servo units can be very difficult to rebuild satisfac=
torily. <br></div><div class=3D"gmail_default" style=3D"font-family:comic s=
ans ms,sans-serif;font-size:small">The symptoms that you describe are howev=
er more indicative of air in the system than those typical of servo difficu=
lties. <br></div><div class=3D"gmail_default" style=3D"font-family:comic sa=
ns ms,sans-serif;font-size:small">If the servo is not working properly the =
typical symptoms are  no servo action at all or brakes dragging and/or lock=
ing on.<br></div><div class=3D"gmail_default" style=3D"font-family:comic sa=
ns ms,sans-serif;font-size:small">To check the servo action pump the brake =
pedal several times with the engine not running then,=C2=A0 with pressure o=
n the brake pedal, start the engine and the pedal should drop a little as m=
anifold vacuum is established. If the pedal drops the servo is working.<br>=
</div><div class=3D"gmail_default" style=3D"font-family:comic sans ms,sans-=
serif;font-size:small">The other problem is evident when you drive the car.=
. First the brake pedal will become quite &quot;hard&quot; and there will b=
e no &quot;free play&quot; at the top of its stroke next the brakes will ge=
t very hot and eventually the car will stop moving because the brakes are l=
ocked on..<br></div><div class=3D"gmail_default" style=3D"font-family:comic=
 sans ms,sans-serif;font-size:small">The usual cause of that problem is the=
 failure of the large piston within the servo unit to return fully to its r=
est position when the brakes are released. That is where the &quot;thinner =
sponge&quot; thing comes in. The correct solution is to have the inside of =
the servo &quot;chest&quot; re-coated with a special slippery coating. Ther=
e should be more information on that way back in the archives.<br></div><di=
v class=3D"gmail_default" style=3D"font-family:comic sans ms,sans-serif;fon=
t-size:small">Hope that helps,<br><br></div><div class=3D"gmail_default" st=
yle=3D"font-family:comic sans ms,sans-serif;font-size:small">Michael S<br><=
/div><div class=3D"gmail_default" style=3D"font-family:comic sans ms,sans-s=
erif;font-size:small">BN1 #174 <br>(4 wheel drum brakes ..no servo)<br></di=
v><div class=3D"gmail_default" style=3D"font-family:comic sans ms,sans-seri=
f;font-size:small"><br><br></div></div><div class=3D"gmail_extra"><br><div =
class=3D"gmail_quote">On Tue, Oct 20, 2015 at 6:24 PM, R. Cobb <span dir=3D=
"ltr">&lt;<a href=3D"mailto:rcobb@earthlink.net"; target=3D"_blank">rcobb@ea=
rthlink.net</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" styl=
e=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Unit wa=
s rebuilt using kit from Moss.<br>
<br>
Symptoms, following bleeding hydraulic brake system (no differences noted w=
hether car running or not): On first try of brakes, nearly no braking, with=
 pedal going almost to floor.<br>
<br>
Second try, sometimes a release is felt in the pedal (with an associated, s=
light &quot;pop&quot; sound) with a bit more braking and less travel of ped=
al.=C2=A0 By the third try, the pedal travel seems more normal, and the bra=
king is improved, though not up to the level expected.<br>
<br>
The above pattern has been replicated numerous times, with the thinking tha=
t perhaps if something were binding, it would work-in. No such luck.<br>
<br>
Any thoughts?<br>
<br>
I recall that some months ago a contributor mentioned having had to install=
 a thinner sponge rubber ring for under the piston seal...because of bindin=
g(?).=C2=A0 Could this be the issue?=C2=A0 Would this result in the behavio=
r I&#39;m experiencing?<br>
<br>
Thanks in advance.<br>
<br>
Bob<br>
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</blockquote></div><br><br clear=3D"all"><br>-- <br><div class=3D"gmail_sig=
nature"><div dir=3D"ltr"><div><div dir=3D"ltr"><i><font size=3D"2"><span st=
yle=3D"color:black">If you can&#39;t fix it with a hammer, you&#39;ve got a=
n electrical problem.</span></font></i><br><br><div></div><div></div><div><=
/div></div></div></div></div>
</div>

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