Any pros or cons in using silicone brake fluid in a 1961? Thanks for the help, Joe
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Re: Silicone Brake Fluid
I use it in my 65.
Pros:
doesn't absorb moisture resulting in rusted out cylinders
(I bet this is more of a problem with disc calipers)
won't remove paint
Cons:
expensive
absorbs air easily
makes bleeding more tricky (peddle a bit soft)
to name a few -
Re: Silicone Brake Fluid
Check the archives. This subject gets beat to death every few months.Comment
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Re: Silicone Brake Fluid
Joe,
I can relate one story to you I heard on another message board. (Can't find it now, or I'd steer you to it). A guy went with silicone fluid in an early Vette. He bled everything and had a "decent" pedal. He went on a run to Denver (lower atmospheric pressure) and completely lost his pedal. They bled them again up there, then when he got home, the pedal was harder than ever before.
Just an example of how the silicone fluid traps tiny bubbles of air. I believe that's it's biggest downside, but I use it in my cars and haven't had any problems. I'm VERY careful not to shake the bottle; I pour slowly and bleed the lines very gently. Also, I do not bleed the master by running a hose back into the reservior. That would only force air back in the fluid. The whole point is to keep the air out in the first place. At least that's my experience.
Maybe others have had different experiences.
Verne.Comment
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Silicone Brake Fluid
I used silicone fluid with new lines and wheel cylinders. After pouring slowly and bleeding the lines carefully, I went to Eisenhauer tunnel (11,000 ft + or -) and had a hard brake pedal. I figured that I had done it correctly.Comment
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Re: Silicone Brake Fluid
Has anyone had experience placing an open bottle of silicone fluid in a vacuum chamber before using it to get the bubbles out?Comment
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Re: Silicone Brake Fluid
I question the "air entrapment" theory for silicone fluid. A fellow Cosworth Vega owner who worked in a lab did some experiments a few years ago and here are the results.
He tested miscibility and found that silicone and glycol fluid are not miscilble. No suprise. Also, glycol-based fluid is miscible with water. Silicone is not.
The specific gravity of silicone fluid is 1.40 vesus 0.95 for glycol based. He didn't have proper equipment to measure viscosity, but silicone fluid does have higher viscosity than glycol-based fluid.
He shook up a beaker of it, waited a few minutes, and then pulled a vacuum on the beaker while observing for air bubbles, but observed none.
He conducted these tests after trying to convert to silicone fluid using the "bleed to flush" method and having a poor pedal.
The bottom line is that you can't successfully convert to silicone using the bleed to flush method. Most who attempt this report poor results. There is no way to completely flush out all the glycol fluid, so this defeats the purpose. You must start with every thing clean and dry, including all the brake lines, then assemble cylinders and calipers with silicone fluid, and finish off by filling the system with silicone fluid.
DukeComment
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Re: Silicone Brake Fluid
I have my '63 going back together with all new brake lines, sleeved cylinders, etc. and I'm still not sure which to use. What do you recommend in my situation?Comment
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Re: Silicone Brake Fluid
Duke,
When I assembled my '65 in 1987, I used newly-sleeved calipers, new rotors, a new M/C, and only new brake lines from the M/C to the brake block and from the brake block across the front crossmember. Not being one to 'do' my own brakes, I had the car towed to a brake shop where they installed the rotors, calipers and M/C and installed the silicone fluid that I provided. Since that time, I have put probably 1500-2000 miles/year on the car and I've never had any problem with the brakes, in particular, no 'soft' pedal. Now I will add that at the time of my purchase of the car, it had been sitting in a relatively disassembled state for probably a year or two, likely with the old M/C and calipers removed and therefore the lines open to the air. Given what you've said about it being 'impossible' to effectively flush the system for conversion to silicone, would you postulate that the remaining glycol in the re-used lines of my system simply evaporated during the storage?
grantComment
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Re: Silicone Brake Fluid
I'll suggest another simple experiment:
Take two clear glass jars and pour some new regular brake fluid in one and some silicone fluid in the other. Now take a straw and blow some air bubbles into each. Observe how quickly the air rises to the top of the standard fluid and how tiny bubbles trapped in the silicone fluid.
Verne.Comment
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Re: Silicone Brake Fluid
I used silicone in my SWC. Be sure to assemble the m/c and wheel cylinders with silicone fluid. If they are new or rebuilt disassemble them, clean everything with denatured alcohol and assemble them with silicone fluid.
New lines should be clean, but flush any reused lines thoroughly with alcohol and be sure they dry before assembly. Also, highly recommend new flex lines at all four corners.
Drum brake cars don't have the water intrusion problem at the piston seals that disk brake cars have, but I would still recommend a system flush every five or six years.
DukeComment
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Re: Silicone Brake Fluid
Glycol evaporates very slowly, so I expect you might have traces left in your system, but if it's operated trouble free for nearly 15 years I don't think you need to worry.
Because the glycol is lighter it will migrate to the top of the system or be trapped in high spots. You might check to see if there is any at the top of the m/c fluid level.
If you have never flushed the system, I would recommend that you do this service. Siphon out the m/c to start and flush about a quart through.
DukeComment
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Re: Silicone Brake Fluid
i have read that vibration will cause bubbles in silicone brake fluid. this would be a good experiment for you guys with silicone fluid and lots of spare time on your handsComment
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Re: Silicone Brake Fluid
Silicone fluid doesn't like to be "agitated", as that makes any entrained tiny air bubbles even smaller (and more of them); that's why it's not recommended for use in cars with ABS - the high-pressure pump and high-frequency modulating pistons "agitate" it and aggravate its tendency to entrain air.Comment
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