[Mgs] Brake filaure

Hans Duinhoven h.duinhoven at planet.nl
Wed May 6 11:33:21 MDT 2020


I can confirm this. Have a friend, who also had phantom leaks, where the fluid disappeared into the vacuum box the the power brake system.

 

Cheers,

Hans 71 BGT

 

Van: Mgs [mailto:mgs-bounces at autox.team.net] Namens Max Heim via Mgs
Verzonden: woensdag 6 mei 2020 18:59
Aan: mgs at autox.team.net List
Onderwerp: Re: [Mgs] Brake filaure

 

I have heard of “disappearing brake fluid” cases where it has been sucked into the booster due to a leak in the master cylinder seal. Normally one would expect it to drip into the footwell, but engine vacuum sucks it in and burns it. In any case, mere bleeding is not going to solve this issue. It definitely went somewhere.

 

--

Max Heim

'66 MGB

 

On May 6, 2020, at 12:23 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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