I've had simillar problems, and I believe that the silicone brake fluid used
by the military holds tiny air bubbles. The smallest jarring of the
container (mine was a 1 gal. plastic jug) caused the fluid to be
"contaminated" with air. The problem is that it takes much longer for the
air to rise up out of the silicone fluid. So, even while pouring the fluid
into the master, you've introduced air. Bleeding the brakes will allow all
of the trapped air in the line to be removed, but not the trapped air
bubbles in the fluid, thus causing a spongy pedal no matter how much you
bleed the brakes. As far as having brakes a week later, but also having a
lower fluid level in the master, it is possible that the air has
precipitated out of the fluid over a period of time (a couple of days), and
exited the system through the highest point in (your master cyl.), thus
lowering the fluid level, and removing enough air from the silicone fluid so
that when you are stepping on the pedal, you are not just compressing the
air in the fluid, you actually move the fluid and the wheel cyl---eg.
properly functioning brake system. (the fluid itself isn't
compressable--just the air in it). I have worked on many M-37's, and I went
through a silicone brake fluid phase, I had one case where I completely
rebuilt a brake system, bled with a brake bleeder, and had a low spongy
pedal. No matter how much I bled I couldn't get rid of the spongy pedal, so
I re-bled the system with rubbing alcohol to remove all old silicone fluid,
then bled them again with good old DOT 3, and got an excellent high hard
pedal. I like the fact that the silicone fluid doesn't absorb moisture, but
I don't think it's worth the trade off. Last thing--All of my CUCV's have
the silicone fluid, and they don't give me any trouble--however, I haven't
done any real brake work on them yet.
David Bobik
Trader John's Outpost
1173 North LaFox Street
South Elgin, IL 60177
phone: (847) 741-3388
fax: (847) 741-2769
e-mail: john@trader-johns-outpost.com
http://www.trader-johns-outpost.com
----- Original Message -----
From: <DDoyle9570@aol.com>
To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
Sent: Thursday, March 15, 2001 7:18 PM
Subject: [MV] brake fluid question
> Two years ago, I bought a M292A2 with silicone brake fluid in system.
> When I went to get it at Ft. Riley, it was full of fluid, but had no
brakes.
> Bleeding didn't help.
> When the lowboy got here (Tennessee), the truck had brakes.
> Drove truck 5-6 miles.
> I let it set several months, no brakes, and low on fluid....added fluid,
bled
> brakes, still no brakes, let set a week, brakes work.
> Let set several more months, drove 1 mile, brakes work.
> Let set one week, no brakes, no fluid, no visible leak.
> Add fluid, no brakes....
> Any ideas?
> Thanks for any ideas,
> David Doyle
>
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This archive was generated by hypermail 2b29 : Wed Apr 04 2001 - 08:10:47 PDT