Silicone brake fluid and rubber door seals

[JHZR2]

Regular brake fluid is hard on paint and who knows what else. What about the dot 5 silicone brake fluid?

Mineral oils are bad for rubber, but silicones seem to be good for all but silicone rubbers. Silicone greases are often recommended for conditioning and preventing seals from sticking...

Silicone greases (pure) are generally 70% silicone oil and then 15% silicate solids (eg silica quartz) and up to 15% other solids.

Pull out the solids and you have poly(DIMETHYLSILOXANE).

Silicone brake fluid is like 95% poly(METHYLSILOXANE).

Doubtful that one methyl group makes a huge difference.

There is a tiny bit of ester and a phosphate compound in there perhaps as corrosion inhibitor.

So... Why not use silicone brake fluid on rubber car seals???

Easier to work with, brushable, not sticky, won't grab dust, no solids, more silicone.

So, what's the downside?

 

[JHZR2]

This has nothing to do with brakes. Alternate use given the chemical structure is the same as silicone grease.

 

[72te27]

Moss Motors has a good tech article on brake fluids. Written for their British car customers, it applies to all.
http://www.mossmotors.com/SiteGraphics/Pages/brake_fluid/page1.html

 

[Donald]

Originally Posted By: JHZR2
Regular brake fluid is hard on paint and who knows what else. What about the dot 5 silicone brake fluid?

Mineral oils are bad for rubber, but silicones seem to be good for all but silicone rubbers. Silicone greases are often recommended for conditioning and preventing seals from sticking...

Silicone greases (pure) are generally 70% silicone oil and then 15% silicate solids (eg silica quartz) and up to 15% other solids.

Pull out the solids and you have poly(DIMETHYLSILOXANE).

Silicone brake fluid is like 95% poly(METHYLSILOXANE).

Doubtful that one methyl group makes a huge difference.

There is a tiny bit of ester and a phosphate compound in there perhaps as corrosion inhibitor.

So... Why not use silicone brake fluid on rubber car seals???

Easier to work with, brushable, not sticky, won't grab dust, no solids, more silicone.

So, what's the downside?


I have used Syl-Glide on rubber seals with no problem. But I would prefer to use a grease than a brake fluid.

But if its a wheel bearing seal, I would just use wheel bearing grease.

 

[Trav]

I lubed the rubber seal in my original Mity Vac hand pump with DOT 5 since i bought it new in 1987. Still on the original rubber seal.
I drew it right out of the bottle with a short piece of hose after i got done using it and flushed it.

I have used it on motorcycle fork dust seals with no ill effects over 20+ years on the same seals.
I haven't found anything yet it deteriorated, i got a big box load of the Belray stuff from a MC dealer who was going out of business years ago for cheap.
I did use in my non ABS bikes but like you looked for other uses for this stuff. It is harmless to paint so i spray my snowblower auger and chute with it, it works great.

 

[JHZR2]

Ags silicone brake fluid is Dow Corning 200 silicone at about 95% fwiw.

Here is the pds:

http://www.chembar.com/content/Dow 200 fluid data.pdf

 

[JHZR2]

I went and bought some of that ags fluid. I'm going to try it on some seals..