[Mgs] Brake filaure

[Richard Ewald]

Blowing/sucking into the hose from the intake to the booster will verify if
the one way valve is functioning.  That it is all it will tell you.  The
described condition is not consistent with a failed one way valve.
A leaky master can leak fluid into the booster. and eventually if the
amount of fluid builds up enough it will get sucked into the engine and
burned.*.  Quite often when the master is leaking like this you can see a
trail of brake fluid and dust on the face of the booster directly below the
master cylinder itself.
the other common source for mystery brake fluid disappearances is the rear
wheel cylinders.  Between where they are located on the backing plate, and
the dust in the rear brakes it can take a fair amount of leakage before any
is visible.  I would suggest  if the booster is dry, you pull the rear
drums and examine the wheel cylinders.  If there is no obvious leaks, be
sure to peel the boots back and check inside.

hope this helps
Rick

* I had a friend that had a Series 1 E Type.  One day he comes out for a
drive and checking under the hood he sees the brake fluid is low.  He grabs
a can and starts pouring.  All of a sudden the car is billowing acrid white
smoke AND the master reservoir is not getting full.  After a couple of
second of Whaaaaaa?  He realized that the master had failed and the booster
was full to the vacuum hose port, so everything he poured in was going
right out the exhaust.

On Wed, May 6, 2020 at 12:49 AM PaulHunt73 via Mgs <mgs at autox.team.net>
wrote:

> I'm not aware that blowing and sucking on any tube at the carb will help
> in diagnosing the brakes.  If you mean the servo hose that should come from
> the inlet manifold but still be no help.
>
> Stomping on the pedal should not put air into the system, if it does then
> there is a fault somewhere that needs to be found.
>
> Is this single-circuit or dual-circuit brakes?  The former should have a
> 'slow-return' valve in the master outlet and with that if a couple of
> quick pumps on the pedal makes the pedal shorter and harder, but then it
> goes long and spongy again if released for a few seconds, that does
> indicate air in the system.  Dual circuit varied.
>
> Unless the fluid level in the master dropped right down to outlet level,
> or you have opened the plumbing anywhere, you should not get air in the
> system by being parked up.  A leak will of course lower the level, could
> possibly allow air in I suppose, but doubtful in my mind.  I've found that
> fluid dropping on a concrete floor 'evaporates' over time.  Check the
> carpets under the pedal as that is another place where fluid goes if the
> master secondary seal fails.
>
> Bleeding method varies according to system type i.e. single or dual.
>
> PaulH.
>
> ----- Original Message -----
>
> I have a power assist brake system which after bringing out of winter
> cover my MGB GT V8 exhibited brake failure  No brake fluid on the floor but
> it did need topping up.   So added Dot 4 but still soft squashy pedal.
> Blowing/sucking  on tube to Edelbrock carb (I have a Rover V8 dropped in)
> it sucked but would not blow (I understand this is correct}.  So we figured
> that the brakes need bleeding - is this a correct diagnosis?  Any tips for
> a non-brake but fairly well versed owner.   If I stomped a lot on the pedal
> when engine running would that put air into the brake pipes
>
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