Re: M35 brakes must be vented

From: noel shelley (noel@shelley1722.freeserve.co.uk)
Date: Sun May 07 2006 - 04:08:02 PDT


Hi Marty ,
                 As to water absorption in DOT3/4 ! Imagine mixing water and
whiskey , it appears as one liquid ie doesn`t separate . Now heat and the
alcohol will evaporate off as a vapour leaving the water !
Whilst liquids are incompressible ( or nearly so ) air or any vapour will
compress easily ! When the brake fluid is heated above 212F any water that
has been absorbed in the fluid will vaporise causing a break in the solid
(liquid ) column and loss of braking at the wheels .
The reservoir must be vented to allow for expansion and contraction due to
temp change and also to allow fluid to replenish the system as shoes or pads
wear

PS for the purists , yes , as the pressure rises so does the boiling point !

                                 best wishes Noel



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