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MG MGB Technical - Brake fluid disappears

Hi all (excuus for my bad tech. english)
I've got a GT '72 now a year and since then also the problem my brake fluid disappears !! first slowly, and now ... after 5km driven again nothing . Begin this year we thought we find the problem on the back brake cylinder which was leak. but now i can't find any place were it's wet. i check all the brakes and as far as possible al the pipes.
does any body has an idea what to / check ??

Wim ,Netherlands

w. kion

Have you checked the carpet in the cockpit beneath the master cylinders? A leak in that master cylinder will seep into the car.

does it have a servo fitted. this can be leaking internally and burns out through the exhaust system.
s curtis

If you have a servo, remove the vacuum pipe & poke a bit of wire into the body of the servo using it as a dip stick.This is where the fluid collects if it's leaking. Barrie E
Barrie Egerton

It seems as though your master cylinder has experienced a seal failure. Briefly, the piston inside the master cylinder wears out over time and allows the fluid to pass and and this wears the seals. The seals in turn will leak and you will lose fluid. In short, it is time to replace the master cylinder assembly. Also check your wheel cylinders for similar failures

Let us know what the outcome of this problem is


Gary :>{
79 mgb

coming monday i will try all of your sugestions to find out if it's one of them.

I allready took off all the weels and checked the cylinders and they were all dry. i don't think it could evaporate away leaving nothing?!

i hope to drive again soon

thanks all for now

100% guaranteed brake servo failure.Another symptom is excesive white smoke in the exhaust. Best to source a replacement or disconnect it from the circuit altogether.
philip may 3

i be phoned this afternoon by my garage, i even had not the time to call him ,....
He told me also to disconnect the servo, there i had to pick up a peace a his place so i can connect both pipes together so i can DRIVE . Braking will be more power using he told me be you can drive then....
I hope to find out more comming monday... On one side i hope it is the servo so i know were the problem is comming from but on the other hand... the cost ...

we'll see..
thanks all
tobe continued

today i made a bypass on the servo..and bleed all the brakes. After a few hundred meter the enige blow an enormous white smoke out ! So the servo isn't part of the brake system anymore.
I have the push more on the brakes now, but they working fine without the servo. I've driven about 50 KM's and the brakefluid is still good.

Thanks all for the help.
w. kion

Should there something be done with the vacuum part of the system ??

Because the vacuum part of the servo is broken, should i do something with the vacuum part of it ??
Can it harm the engine (if still connected) ?? Should i close the hole or vacuumpipe ??


w. kion

If the engine has been sucking in fluid from the servo, and you have now disconnected the brake lines from the servo, it will now be sucking in air. Disconnect the vacuum hose from the servo and plug it.
Paul Hunt 2

w. kion

This thread was discussed between 01/06/2006 and 12/06/2006

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