[Healeys] troubleshooting rebuilt Girling BJ8 brake servo

[Michael Salter]

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 at 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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