The Stovebolt Site Forums The Shop Area Driveline silicon brake fluid ?

I need your advice. I have rebuilt entire brake system, new dual master, new slaves and line along with pads and all hold down hardware. I was contemplating dot5 fluid since the system has not seen any fluid yet. What do you guy's think? Have any of you moved to dot5 from dot3 and if so how did it work out. Your opinions are greatly appreciated.

Don't do it. Leave that stuff for the Harley and British car guys. I tried it in mine after a complete rebuild, it worked fine, but I kept having this mysterious spot on the floor that I couldn't identify where it was coming from. Turned out that the MC was leaking. After futher inspection, i found that both front wheel cylinders were leaking, too. These were new parts. It turned out that the dot5 fluid wasn't compatible with the rubber. Had to change out the seals. Put in dot3 and haven't had a problem since.

Do all the rubber parts in your system specifically say on them or on the packages they came in that they are OK for Silicone fluid?

If you don't know then stick with the regular stuff.

I worked in a restoration shop for a while, and a customer insisted on using silicone fluid in his old car. We did do a complete brake rebuild, stainless sleeved cylinders, all new lines, and the new rubber parts, but no choice on silicone compatibility or not. We spent hours on hours fighting leaks that would have not have occurred if we had used the regular fluid, or had silicone compatible parts been available.

Grigg

For you to avoid the commonly experienced leaking in brake systems using silicone, you must do the following (as stated above):

(1) use new rubber parts (if not all new parts); and,

(2) check with the manufactures of all the new components (that have rubber parts) to find out if all parts are compatible with silicone fluid.

Doing #2 is very difficult. Often manufacturers do not want to say their parts are all "silicone friendly" because they cannot be sure your whole system has been set-up properly, and they cannot be certain that your parts-store will have new-enough stock that has silicone-friendly rubber (Jim Carter did not, a few years ago when I used a new master cylinder that failed).

I have had silicone fluid in my '54 Suburban for several years, with no problems. It had all new brake parts, and I persisted in obtaining information that all rubber-containing parts were "silicone friendly". However, I will not be doing this on the two trucks that I am now restoring because it's not worth the time and effort. I'll be bleeding and servicing the brakes of these trucks so often that there would be no additional benefit from using silicone fluid.

Tim

Thanks guy's, thats just the real world info I was after. Ill stick with dot3, I flush it out on my sports cars every spring so I will just do the truck at the same time. Thanks again.

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Search the forums, it has been covered to death. Stick with DOT3 and you will be fine. Just keep flushing like you are supposed to do. For those that do not flush, DOT3 and DOT4 are hydroscopic (absorbing moisture from the air). DOT5 is generally used in racing applications for the higher temperature requirements.