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MG MGB Technical - Servo Problem


I have lost all brakes on my '74 B roadster whilst it has been sat in the garage avoiding the salt. Got it out and no brakes.

1: Noticed that the pipe connecting the brake servo to the inlet manifole of the engine was frayed. I cut this pipe to ease removal and found it had a small amount of liquid with a similar consistancy to dot 4 in it. The liquid was contaminated and contained bits and black filth but this could have been from when I cut the pipe. Should this pipe have this black liqued or indeed anything in it?

2: The brakes should work without the servo (right?) they will not be as good but they will still work... so as I have litrally no brakes at all (on the pedal the hand brake works) that can't be the servo.

Please help!!

Thanks.
C Beswick

Hi

Is the brake pedal hard, very soft or somewhere in between ?. A non working servo (eg if the vacuum pipe leaks or collapses internally) makes the pedal go quite hard, and makes quite a difference to the braking effect. I certainly wouldn't attempt to drive a car (even slowly) with a faulty servo.

With the engine not running, pump the brake pedal a few times to get rid of any remaining vacuum, then, with your foot pressing the pedal, start the engine.. the pedal should drop slightly as the servo starts doing it's job.

It sounds as if the servo may be leaking internally, allowing brake fluid into the vacuum pipe (which should be empty).

Has the car been mysteriously using brake fluid ? (ie the level goes down but you can't find where it goes).
You may find that the brake servo canister is partly full of it.

Don
Don

As Don notes, a faulty servo will not cause brake failure. A bad master cylinder can leak fluid into the servo unit. Do not know if you have the servo on the pedal box, as the US cars do, or if it is a remote servo. If you have no brakes, you need to remove the master cylinder and servo unit and inspect both of them. Les
Les Bengtson

The appearance of brake fluid in the brake servo and then into the vacuum hose is a common fault.
You have leaking Master Cylinder seals.
The only place brake fluid can come from is the Master Cylinder. It is not a servo fault, as there is no fluid in any part of the servo during normal operation.

Mick
M F Anderson

Have you fluid in the master? If it *is* brake fluid in the vacuum pipe then the servo is bad and you have probably been burning the fluid in the engine or the servo is full of it. On the other hand it could be that fuel from the inlet manifold is rotting the rubber and producing a black goo of similar consistency. MGB brakes are fine without servo, it is surprising how little boost it gives. If the master is empty the fluid must have gone somewhere, if it isn't on the carpet or the ground then the servo is probably to blame. I'm assuming a remote servo same as on my UK 73 and 75, hence a servo problem and not seals in the master cylinder.
Paul Hunt

This thread was discussed between 27/01/2003 and 28/01/2003

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