I put silicon in many of my cars back in the early 90s including my C-300. This resulting in me having to change the brake light pressure switch every two years until I switched to one from H-D motorcycles made for silicon.
I do however believe that silicon fluid is more compressible than DOT 3 and 4, giving a softer pedal. In another car I experienced bottoming out the pedal when doing a panic brake stop, so maybe the theory of small bubbles can be applied. I have also seen evidence of trapped water in silicon filled systems, creating the dreaded rust.
When I had the M/C rebuilt some years back I was told not to use silicon in it, and duly switched. Since then my brake feel is firmer and I plan to bleed the brakes and partly replace the fluid every 3-5 years. No new rust spotted yet.
Narve in cold Norway
I have a G that I put silicone fluid in it about 40 years ago and never had a leak in a wheel cylinder or the pressure brake switch until after it was in a body shop getting rust repaired for 4 years. At that point a wheel cylinder failed. I don't recommend going 35 years without changing the fluid, as had I changed it every 10 years or so, that cylinder would likely not have failed. I am replacing the master and wheel cylinders and will use silicone fluid again. I use Dot 3 or 4 in my drivers and change the fluid when I replace brake pads. If I put Dot 3 in my G I would change it every year or 2 max. I will probably never wear out the shoes on my G as I doubt I will drive it that much. I will change the silicone after 10 years if the virus doesn't get me first. I mentioned that silicone had not affected my pressure brake light switch before on here and someone wrote me back saying that G's didn't have a pressure switch. My car was delivered in November 1960 and is equipped with a pressure switch.
Loren Nelson 300G in spring blooming N Georgia
Posted by: "Narve Nordanger" <flathead323@xxxxxxxxx>
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