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Re: [TR] Why brake fluid rust resevoirs?

To: "Paul Dorsey" <dorpaul@negia.net>,
Subject: Re: [TR] Why brake fluid rust resevoirs?
From: John Wise <60TR3A@cox.net>
Date: Fri, 26 May 2006 19:14:56 -0700
At 8:24 AM -0400 26/5/06, Paul Dorsey wrote:
>Why is it our Master Cylinder resevoirs aren't eaten up with rust on the
>inside?  Particularly, at the top of the inside (the area that sees repeated
>wet-then-dry)?
>
>During my restoration, I took my dry one inside the shop.  Several years
>later, I've noticed some light rust spots trying to form on the inside that
>was previously shiny.  So I took some clean nuts from my bolt collection,
>cleaned them first, then put about 20 into the can and shook them around a
>bit.  Then I rinsed the resevoir out good with clean brake fluid, doing so
>twice.  However, it maybe weeks before it will permanently be holding DOT 4
>brake fluid.

You need water for rust.  Brake fluid is not water so it does not 
support the development of rust.  However, traditional brake fluid is 
hydroscopic  (sp?) which means it absorbs water from the atmosphere. 
Overtime traditional brake fluid absorbs enough humidity that the 
water (which is heavier) ends up at the lowest part of the brake 
system & which supports the development of rust at those points where 
the water sits.

The other down side is that when the brakes get very hot (e.g., 
racing or very spirited driving) the water turns to steam which is 
compressible & then you get soft brakes.

John
-- 
John A. Wise
Glendale, AZ

Email:  60TR3A@cox.net

1960 Triumph TR3A
Commission No: TS80422L
http://members.cox.net/60tr3a/index


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