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Re: Brake servo

To: CoolVT@aol.com
Subject: Re: Brake servo
From: Steve Laifman <laifman@flash.net>
Date: Tue, 06 Oct 1998 07:33:43 -0700

CoolVT@aol.com wrote:

   I rebuilt my brake servo 4-5 yrs. ago and it was great for a few years.  Last
   year it swallowed up all the fluid (no visible leaks).  What part should have
   been replaced and was not included in the rebuild kit?   It seems like 
someone

   on the list mentioned something about ceramic disks or something of the sort.
     Where are these needed parts available?   Thanks in advance.  Mark L.


Mark,

You didn't mention which "Mark" booster you had, but I'll assume it's a Girling
MKIIA.  Don't think ceramics were used in GB in the
60's for anything more technical than a W.C.  The major leak of fluid is usually
between the shaft on the "vacuum piston" inside the coffee can and the hydraulic
system pistons.  There is a vacuum on one side and fluid on the other.  This
shaft moves back and forth on an
elastomeric seal.  when it wears enough, there's plenty of suction to 'eat' the
fluid.

I have heard that only Girling LMA (no longer made, but still available, Lucas
substitute listed) won't eat English seal rubber, but don't
know for sure.  I'd examine the condition of that push-rod for wear and scoring.
Maybe a hard chrome plating and polishing  would
extend the life.  The push-rod is attached to a coffee can lid of 5 to 7 inches
in diameter called a piston.  It rides on the inside of a coffee
can that holds the vacuum.  A greased rope is set between them to act as a seal
as the lid moves back and forth in the can.  This rope is
usually too long in the rebuild kit, and  must be trimmed to a perfect
(unspecified) length to make a good seal.  It is lubricated with another
very exotic Girling red jam.  Almost enough is supposed to be supplied in the
kit.  This balances the extra rope.

I have been looking for someone to install honed stainless steel sleeves in the
booster and MC to no avail.  Some want to do it in brass.  I
guess that's ok too.  A polished hard chrome on the coffee can interior might
make for a longer lasting bore.

Besides, 4 to 5 years is pretty good for something that was designed in 1932.
The MkIIB used a rubber diaphragm as a "piston" like the
'Murican cars, and was a better design, overall.  Fit the car fine.  Can't get
rebuild kits for them, and if you can they are over $350 for the
kit.  Besides, they weren't original.

--
Steve Laifman         < One first kiss,       >
B9472289              < one first love, and   >
                      < one first win, is all >
                      < you get in this life. >


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