Date: Sat, 24 Feb 2001 06:00:48 -0800
From: Greg Nelson <gregsays@swbell.net>
Subject: Re: Replaced Nylaflow with Aeroquip 303 & have problem
To: lancair.list@olsusa.com
Message-id: <3A97BE90.3760A539@swbell.net>
References: <20010224023439.13573.qmail@web1702.mail.yahoo.com>
Reply-To: lancair.list@olsusa.com
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Tom Harris:   Yes, definitely! This from the builder that has made every
mistake twice...

I originally equipped my brakes with 303 hose in the lower 18 inches of
length because the brake fluids made hot during braking would not then
contact the Nylaflow.  This worked fine in my original installation
using only hydraulic fluid but I wasn't satisfied with using hydraulic
fluid for braking so I switched fluids to "DOT 4".  DOT 4 is labeled as
being "silicone" as I figured this would be superior to hydraulic fluid
if only because its vapor pressure is about 125 degrees higher than that
of hydraulic fluid   (If fluid should vaporize in a brake line, the
brake would either lock up or else become extremely spungy.)

Long story short, it didn't work!  Using DOT 4, the brakes became
totally spungy so that brakes couldn't hold even at quite low engine
RPMs. We (I sought competent counsel from a fellow Lancair builder Don
Ryan who is a chemical engineer) deduced that the problem was probably
not caused by the 303 hoses alone but rather by the combining of 303
hose material with the DOT4.  The problem seems to be that the DOT 4
fluid is very severe (eats up) some materials including specifically
teflon and the 303 hoses are Teflon lined.  We concluded this upon
observing that Teflon tape disappears quickly when wetted with DOT 4.
We suspect that certain seals, etc. of the MATCO brake system are also
of Teflon.  Perhaps too, another material (Nylaflow itself??) is
incompatible with DOT 4.

In any event, we had to restore all brake lines back to the original
materials and specs designed by Lance and they now work fine.  We
believe too that mixing of fluids and materials runs risk of damaging
the brakes.

We called MATCO to discuss this finding and they offered that they had
no previous reports of DOT 4 being caustic to their hardware and that
may be true because the DOT 4 may be attacking the Nylaflow or else the
Teflon lining of the 303 hoses...or some other brake material entirely.

So, don't use DOT 4 in Lancairs unless you want to totally redesign
(experiment with) the brake system and don't mix materials and fluids
within the brake system.                Greg Nelson

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