From: noel shelley (noel@shelley1722.freeserve.co.uk)
Date: Sat Feb 11 2006 - 06:32:52 PST
Robin and the list ,
A word of caution about draining and refilling
brake systems !!
DO NOT enter into this operation thinking that all you will have to do is
refill the system. All too often on older vehicles a system that has been
working fine will fail when you try to bleed the system due to the failure
of the master cylinder seals!!!!! This would seem to be caused by the foot
valve/non return letting in tiny amounts of fluid fine but when opened full
to bleed , give up the ghost !! This may just involve some small expense and
inconvenience, or a major disaster if the seals are unobtainable .
DOT 5 being a silicon fluid does not absorb water and should in theory not
need to be changed as is the recommended practice for DOT3 or DOT 4 , and
earlier fluids .
In 40 years of working on vehicles , I have only once ever come across brake
failure due to moisture absorption in DOT 3/4. It involved complete loss of
brakes at the time ! 2 hours later when I inspected the vehicle the brakes
now worked fine , the steam had condensed and been reabsorbed , leaving NO
TRACE of the failure !!!!!
Good Luck Noel
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