RE: DOT 5 (Silicone) Brake Fluid

[Don Hoefer <hoefer@eng.pko.dec.com>]

Ron says:

>  I know what some people say but, here is my .02.... I have used DOT5 for a
> number of years in some rarely used cars I have owned such as an origional
> Avanti and a number of Corvettes I have owned as well as my 85 Carrera. The
> reason I use it is the fact that it doesn't attract water as you mentioned.
> I had a number of calipers and master cylinders go south from water
> corrosion in a number of these cars.

This is where DOT 5 brake fluid is normally used.  Cars such as these are
usually rarely driven and are stored in controlled conditions (or at least
not out in the weather.

Quotes Douglas:

> DOT 5 fluid is supposed to be superior, including but limited to the 
> fact that it is not hygroscopic.

This is it's saving grace as well as the problem.  Normal brake fluid absorbs
water thus lowering it's boiling point and raising it's freezing point somewhat.
Water that gets into a DOT 5 filled system will "puddle" or collect, creating
pockets of water that can boil or freeze in place.  This is not what you want.

Thus it makes sense to use DOT 5 in museum cars because they will not be
exposed to much moisture and if any gets in, it will not be distributed
evenly throughout the system and cause corrosion everywhere.  I have also
heard that people that do use DOT 5 for racing applications change it very
often.

Anybody else have any knowledge to add or correct?

Don Hoefer
'82 Coupe