I'm with you John, if they can make seals that stand up to hydraulic oil in car jacks, lifts, forklift trucks for years, why not brake systems? Sure, older rubber parts may not have been compatible, but what about modern seal material? I've had a hydraulic car lift in my shop since 1989, never had a leak or had to add fluid. Not to start a huge discussion here, but, I too use silicone brake fluid and swear by it, have had it in my 300G since 1978.
The only thing I can think of, beyond potential rubber incompatibilities, is that brake engineers like the idea of a fluid (DOT 3,4) that is hygroscopic, that is, it absorbs moisture throughout the fluid, and keeps it from settling in low spots, and gradually lowers the boiling point of all the fluid. This eliminates points were water can puddle that could boil, turn into a gas, and result in brake failure. Also, corrosion would be reduced because the fluid absorbs the water. But the down side is it is always there sucking moisture into the fluid unlike hydraulic oil or silicone fluid, and needs to be bled every 2-3 years. I've gone as long as 18 years with the silicone filled brake system in my G without flushing the brake system, until I noticed the car pulling a bit to one side. Once I noticed that, I pulled the front hubs and saw that the lower cylinder on one side began to leak. Removed the brake cylinder, inspected it and found corrosion at the lowest point, indicating the presence of water causing the corrosion. I rebuilt the system, had the wheel cylinders resleeved with brass, refilled with silicone fluid. Now I bleed about every 7-10 years just to be safe, but it sure is better than every 2-3 years. I have heard from other club members that have converted to silicone fluid in the late '70s and not bled since, but I don't know how often those cars are driven.
I do not understand , never did , advantage of brake fluid in brakes ? Why not hydraulic oil , like construction equipment ? Temp resistance maybe , but water in brake fluid boils . Maybe it was the rubber at the time ( 1920's ) deteriorated in oil . Not now with right stuff .( except German rubber) ( MB junk) Might relate to the change in top cyl fluids in 62 . Better seals , oil resistant, allow oil. Atf and ps fluid are both essentially 10 W oil with additives . Semi auto trans was 10 W .
I use silicone exclusively in brakes because military says to . Good enough for me . But silicone oil is like 10 W oil physically . But it loves rubber and other way round . Biggest issue is $ but you can find mil surplus by the half gallon .
Maybe one of our mopar engineers knows "why brake fluid ? " .
If you do not change religiously in MB brakes fail as in 2000$ worth of fail . Yet I had 37 Packard with original brakes when I bought it that still worked ok . Strange stuff ...
Posted by: "Bob Jasinski" <rpjasin@xxxxxxxxxxx>
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