[MV] Silicone Brake Fluid & Rubber

Robert Bell (rbell@erskine.edu)
Mon, 01 Dec 1997 15:52:13 -0400

Alan Bowes wrote:

>DOT 2, 3, 4, and 5.1 glycol fluids are capable of dissolving several
>types of rubber. DOT 5 silicone fluid won't dissolve rubber (as far as
>I know), but it doesn't dissolve paint, either.

My response is not about the use of brake fluid to remove paint, but
about the problem of some brake fluids dissolving rubber; particularly
silicone brake fluid. In the past there has been a rather long thread
on the merits of using silicone brake fluid in MVs. After reading those
messages I had decided to use silicone fluid in my '43 Federal truck in
which I am replacing all lines, cylinders, etc.

This past week, however, I contacted a couple of brake master cylinder
rebuilders about rebuilding a master cylinder for my truck. Dapp
Enterprizes' year-long guarantee is conditional upon NOT using silicone
brake fluid, stating that it turns some rubber to gel. They've had some
re-built cylinders returned within three days all gummy & gooey due to
silicone fluid being used.

White Post Restorations also does NOT recommend the use of silicone
brake fluid. Billy Thompson (owner) states that it may work fine in 9
out of 10 cases, but really creates a mess sometimes. They used
silicone in a few vehicles which they restored, but soon abandoned its
use because where it dissolved the rubber, the entire brake fluid system
had to be replaced. Plus, he states that it is more difficult to bleed
the wheel cylinders and gives a spongy pedal.

I have abandoned my intention of using silicone brake fluid in my
truck's braking system.

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