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Switching to DOT 5

To: "Spitfire List" <spitfires@autox.team.net>
Subject: Switching to DOT 5
From: "Jeff McNeal" <jmcneal@ohms.com>
Date: Thu, 6 Jan 2000 10:45:57 -0800
Hi all...  I currently have no brakes because there's a leak somewhere in
the hydraulics.  The previous owner was using standard (I'm assuming DOT 3)
brake fluid in the reservoir, although he used only Catrol Girling in the
clutch (thank goodness!).  I don't know if natural rubber is used in the
brake and wheel cylinders, but I'm guessing they do and that the use of DOT
3 smoked the rubber seals.

I'm replacing the rear wheel cylinders with brand new ones from Spitbits and
also ordered a rebuild kit for the master cylinder and another rebuit kit
for the front caliper pistons.  I've decided that this might be an excellent
time to convert to DOT 5 silicon, so I've ordered a quart of that stuff from
Victoria British.

My questions are as follows:

Is my assumption that using DOT 3 in the brakes thereby destroying the seals
valid?  Or do the brakes not use natural rubber seals anymore?  Nigel was
unable to tell me whether or not the specifications for the seals have
changed over the years, but I suspect that the original specs still apply.

Will a quart of fluid be enough to bleed the system properly?  I sure hope
so.  That silicon stuff is expensive!!

Is there any reason I should NOT go with DOT 5 silicon and simply stay with
DOT 4 Castrol Girling?  I understand that the silicon fluid might be a
smarter bet for someone like me who will not be using the car as a daily
driver.

Thanks!


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