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Re: Brake Fluid

To: Agustin de la Calle <delacall@bcmp.med.harvard.edu>
Subject: Re: Brake Fluid
From: Chip Old <feold@umd5.umd.edu>
Date: Wed, 14 Sep 1994 00:07:22 -0400 (EDT)
On Tue, 13 Sep 1994, Agustin de la Calle wrote:

> I remember vaguely a helpful posting about the different brake fluids, 
> i.e. DOT3-5. And I think having read that DOT3 would destroy rubber seals 
> with time. Is that correct? My Haynes manual for MGs says I should use 
> DOT3 as brake fluid. Isn't that odd?
 
Not odd at all.  Conventional Wisdom in BritCar circles says that DOT-3 
fluid will rot the rubber parts in a British brake system, but it just 
ain't so.  As far as I can tell, this is a holdover from the days when the 
quality and content of brake fluid wasn't standardized, and any fluid 
containing mineral oil really would rot the rubber.  That's why really 
old BritCar manuals say something like "Use only genuine Lockheed" or "Use 
only genuine Girling".  Later on, the manuals started adding "...but in 
the United States DOT-3 fluid may be used" or something to that effect.
 
DOT-3 (and 4 & 5) fluid is made to very strict specifications to be
compatible with all rubber parts, natural or synthetic.  It will not rot
your rubber parts.
 
For what it's worth, until recently I never used anything but DOT-3 fluid
in any of the many BritCars I've owned, and I've never had a probem with
it.  Recently I've been using Castrol GT/LMA fluid (DOT-4) or silicone
fluid, but only because they are less likely than DOT-3 fluid to absorb
moisture (which leads to rust and corrosion in _any_ brake system, British
or otherwise). 
 
-----------------------------------------------------------------------
Chip Old              1948 M.G. TC  TC6710  NEMGTR #2271
Cub Hill, Maryland    1962 Triumph TR4  CT3154LO (daily transportation)
feold@umd5.umd.edu



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