Subject: [Tigers] Update on DOT 3 - 5

From: Jay Laifman <[email-masked]>
Date: Mon, 22 Apr 2013 22:12:52 -0700

I should have spent more time in the archives.  I found plenty of information,
including from my dad.

DOT 5 is no more or less "compressible" than DOT 3 or 4.

Silicone fluid does not absorb water.  So the same water that gets into the
system accumulates at low spots and therefore makes the greatest chance of
rust at that spot.  This is of course an issue in the brake system, whereas
the clutch's lowest point is aluminum!  But clutch or brakes, that pocket of
water in DOT 5 is worse for spongy brakes when it heats up in there and the
water steams, and not so bad when it is spread out in DOT4.  DOT 4 accumulates
some sort of brown gunk, needing flushing every couple of years (which really
isn't a problem) but DOT 5 does not.

Apparently that is why my dad put in an accordion moisture block on top of the
reservoir.  So, the fluid level can go down (like when you press the clutch)
without sucking in moisture through the hole.  Kind of the best of both
worlds

There are opinions back and forth about what fluids swell the rubber now and
which ones don't. Some suggest to soak the rubber in DOT 4 before installing
in a silicone system.  But, then there are people who say the fluids have to
be 100% separated and cleaned out.  So, I don't understand this contradiction.
There are people who say it is ok to go from silicone to DOT 4, by just
bleeding a couple times, but not the other way around.

I have two rebuild kits and DOT4 LMA on the way from Rick.  But, with this all
in mind, I think I'm likely to follow what my dad did, and put the silicone
DOT 5 back in.  But, I'm going to mark the top of the cap for my kids!
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From: "Smit, Theo" <[email-masked]>
Date: Tue, 23 Apr 2013 13:36:22 +0000

Silicone fluid is not inherently more compressible than DOT 3 or 4, but it
retains trapped air for much longer and silicone fluid can also absorb air.
That means if you shake the container or pour it such that air is entrapped in
the fluid, it can stay there in a way that is not visible and then when you
bleed the system, it will end up inside the lines and give you a spongy pedal
feel.

http://www.mossmotors.com/SiteGraphics/Pages/Brake_Fluid/page4.html

Theo

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