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MG MGB Technical - Brake booster

my brake booster has developed a leak. While waiting for a rebuild kit, I'm going to disconnect it and plug the manifold hole and the booster hose. Other than increased brake effort, are there any bad effects doing this?
John

Not that I am aware of....I ran my MGC for two years without the brake servoes. Only side effect was my right thigh is now much larger than my left leg! ;-)

rick
1969 MGC
1978 MGB
1974.5 MGB GT V8 conversion
rick ingram

Hi, I think my power booster on my 1976 mgb does not work! I have tried driving with and with-out it,no difference!
It looks difficult to remove,especially removing the pin in the pedel assy. How do you get to it??
The nuts holding the carriage assy. to the body looks impossible!

Some suggestions would help.

Thanks Chuck
Chuck

The brakes are the same on the MGB whether it was built with a servo or not. So the brakes will be just fine without the servo in circuit. They will need a firmer press of the pedal, but the difference is less than you might think.
Mike Howlett

Chuck. I suggest a beer. Sit back and relax a little. Think about this. Your brakes are, it would seem, working for you. As Mike notes, the loss of the power assist only means that you have to press the pedal a little harder than you would have to if the servo (booster) was working correctly. This might be a problem for some women. But, my older daughter has driven one of my cars, a 79, when the brake booster was not working and found she had no problems with it--it just took a little getting used to as compared to her 77 with a working booster. This is not, for the vast majority of people, a safety related problem.

It is, however, inconvenient and most of us, as Enthusiasts, take a degree of pride in how well we have learned to take care of our cars. Thus, in spite of the fact that the system will work when the power booster (servo) is inoperative, we want the system to work properly. No problem with this. There is a rebuild kit available (Bob Ford, at Brit-Tek is an excellent individual to deal with--personal knowledge, and Gordon at the Bee Hive has an excellent reputation, but I have not used his services myself).

Installing the rebuild kit requires tooling that was never made available by the factory. The tool illustrations, along with specifications, are in the factory workshop manual. The tooling was to be custom made, at the dealership or a local machine shop, if a servo unit had to be rebuilt. The need for such tooling, while the final version of the MGB was in production, was minimal. I find the servo unit (brake booster) a long lived system.

Removing the servo unit from its position between the brake pedal and the master cylinder is a bit of a bear, not not a major one. I have done several and, while it is not a job I look forward to, it is not all that difficult. You have to remove the pedal box cover to get at the clevis pin between the brake pedal and the servo unit. Good idea to order a new clevis pin when ordering the rebuild kit. They are frequently badly worn as is the connecting piece between the servo and brake pedal (push rod). A new push rod is included in the rebuild kits I have used in the past. In place of the cotter pin (split pin to the Brits), I have used a "hair pin clip" a smaller version of a "hitch pin clip" which looks something like the women's "bobby pin" . Easier to install and, over more than ten years of use, I have never had one come out unless intentionally removed. I use them in place of cotter pins in both the brake and clutch systems.

I have parted out several rubber bumper cars over the years and have the luxury of having a spare servo around in my parts locker. When I need a rebuilt servo unit, I rebuild the spare servo, remove the old servo, install the rebuilt unit, and move the old servo to my spares lockers. This procedure works very well as it allows me to unbolt the master cylinder from the old servo unit, move the master cylinder forwards, unbolt the old servo unit, replace it with the new servo unit, bolt up the master cylinder to the new servo unit, and hook up the servo to the brake pedal. No draining, refilling, or bleeding of the brakes required the few times I have had to do this.

Thus, I would recommend you obtain a good, used servo unit for rebuilding if you decide to attempt to do a repair. My friends, Bob and Gil Schaulin, operate what has become known as "The MG Wrecking Yard In Arizona" and have a large number of spare parts available, along with a number of years of experience working on MGs. They can, should you wish, supply you with a spare servo unit for rebuilding and provide the rebuild kit at the same time. Not "over educated barstids," like myself. But, I have dealt with them for over 20 years and they are quite knowledgeable, fully trustworthy, and some of the finest people I know. Their telephone number is 602-415-1846 and you can feel free to mention my name.

About the tooling needed. If you decide to perform this task, you might want to contact me through my website, www.custompistols.com/ where there is a contact me feature. I have, in the past, loaned out the tools to do a clutch replacement and to do a power brake booster rebuild. In such cases, the people borrowing the tools sent an "honorarium" when they returned the tools.

I have been, since the tooling is too expensive to manufacture for most people to be able to afford--at least on a non-professional basis, toying with the idea of setting up some form of tool rental system to allow people to have access to the proper tools while not having to spend several hundreds of dollars to have them produced for a once in a life time use. If there seems to be sufficient interest, I will do so, requiring some form of deposit and some appropriate fee for their use.

But, in the mean time, the task you are interested in performing seems more complex than it is and, when one actually puts wrench to nuts, can be accomplished in a single day.

Les
Les Bengtson

Mike may be thinking of the remote servo on single line systems that the UK had until 1977 which *is* marginal as it was optional and so the brakes had to be acceptable without, I have experienced with and without on this system. From what several people have said in the past loss of servo on the master with integral servo is a very different kettle of fish resulting in much higher pedal pressures to stop. I haven't experienced both with this system.

There are two ways of testing the servo, one is to press the brake pedal up and down shortly after having swiched off the engine, and initially there will be a wheezing sound and the pedal movement is 'normal' then after a few presses the wheezing fades away the pedal gets noticeably higher. the second is then to press down hard on the pedal when starting the engine and you should feel the pedal go down a bit.
Paul Hunt

Paul is right, as usual. I was talking about the remote servo that sat on the top of the bulkhead (firewall). I have fitted the in-line direct acting servo assembly to my current 1969 MGB and would say the servo effect is much more noticeable, but I have never driven this set up without a booster.
Mike Howlett

I wonder if anyone can help me. I've owned a GT for a week so I don't have a feel for what the brakes are supposed to be like. I have not been able to lock the wheels in a stop yet.
Secondly, on returning from its first real run I came to the conclusing there was something not right with the brakes. My foot will go all the way down to the floor but there is no fluid leak visible. The level in ok, but when I do foot the brake all the way to the floor, some fluid is evident on the top of the reservoir. When I rev the engine to get more vacuum the pressure on the pedal is better but soon fades. Since I can't see a hydrolic leak could it be the servo that's faulty?
Russ

What age is your car Russ? Does it have the remote servo on the passenger's side of the engine bay, or the servo mounted between the pedals and the master cylinder?

The remote servo can cause hydraulic problems, the in-line one shouldn't. Its also worth looking at the three flexible hoses to the front wheels and the rear axle. If they are old and degraded internally then they can balloon under pressure giving the soft pedal feeling.
Mike Howlett

You should *definitely* be able to lock the front wheels with *progressive* braking, let alone banging them on which locks them easier. Having said that cars of this era are heavier i.e. need more effort than most modern machinery.

Revving the engine actually results in *less* vacuum, not more, the only time you get more vacuum than when idling is when you are on the overrun. As well as Mike's observations I'll repeat that the remote servo gives very little assistance, whereas loss of the integral one can make the brakes significantly harder. But in both cases the pedal should *never* reach the floor, just become very hard.

Does the pedal 'pump up' if you give it a couple of quick strokes? If so they need bleeding.

If the pedal doesn't go straight to the floor but sinks under continuous pressure, and there are no leaks, then the master pressure seal is faulty. If you have a springy pedal then as Mike says the hoses can be ballooning.

Poor adjustment of the rear shoes and handbrake cable will cause long pedal travel.

Never buy a car without it being subject to a *new* MOT from a reputable garage, don't rely on the fact that the existing one has six months to run, or even eleven months.
Paul Hunt

This thread was discussed between 04/06/2004 and 09/08/2009

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