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MG MGB Technical - brakes, vacuum assist

hi
79mgb
help !

my vacuum assiated brake box has failed.
moss doesnt list replacement parts for it.

what can one get as a replacement??

john
john sutter

Stronger leg muscles?
Chris at Octarine Services

Nice response Chris. RAY
rjm RAY

John. As Chris notes, the brakes work fine without the vacuum assist unit. Somewhat harder to operate, but not all that difficult for most people.

I do not know if Moss has quit carrying the servo repair kit, part number 182-205, or not but you might try and see if they are just out of stock or if they have been discontinued.

If you do find a kit remember that you need to make the tools to do the repair as they were never available from the factory. The tools are illustrated in the factory workshop manual, along with dimensions for making the finished tools.

Les
Les Bengtson

I assume your car has the servo in-line with the brake master cylinder, and twin brake circuits (rather than the remote servo over on the passenger side of the car). Moss over here list both the servo itself BAU1016 for £132.95 and the servo repair kit 18G9080 for £73.96. See here http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=17

I don't know what special tools Les refers to. I put a service kit into mine with no special tools at all. The job wasn't hard and it works perfectly. However, as Les says, the brakes are OK without the servo. Hope this helps.
Mike
Mike Howlett

..as Chris and mike write but if the unit is leaking air back into the engine you may have a small problem, more if you have fuel injection.
R
Roger W

Stronger leg muscles indeed. Whilst the remote servo does add very little assistance and can be dispensed with, North American spec cars never got it. But in any event after 76 all cars had the combined master and servo, and I've heard tell that gives much more assistance, and so is a a completely different kettle of swimming things if it fails.
Paul Hunt

Paul. Having used the system with a non-functional servo, then rebuilding the servo and comparing, I consider the servo useful but not essential. Women, however (and, perhaps, men with weaker legs) find the servo quite desirable. It does take considerably more force to operate the late model cars, with non-functional servo units, than it does to operate the brakes on my 68 which never had a servo system. Thus, I would recommend restoring the servo to proper function if at all possible.

Mike. The factory workshop manual, section M.11, under "Dismantling" has as the first entry:
"NOTE" Special tools should be mad for the dismantling and assembly of the servo, see Fig. M7, Fig. M.8, and Fig. M.9.".

Having rebuilt several servo units, after having made up the required tooling, I would hesitate to recommend that someone attempt a rebuild without using the factory specified tooling. At least, not without a spare servo unit to practice on. I have never been one to trust to luck.

Les
Les Bengtson

We've got two relatively modern Euroboxes, both, in my opinion, vastly over-servoed, so the servo in my '77B avoids the panic when first driving it after driving the others, and probably saves me over-braking and maybe getting rear-ended, when going back to them (bearing in mind the French tendency to tail-gate).
John Bilham

This thread was discussed between 25/07/2013 and 26/07/2013

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.