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Re: SILICONE BRAKE FLUID -GOOD OR BAD ?
Posted by: Melb-Mike ()
Date: May 15, 2017 02:31PM

The nice thing about converting to DOT 5 silicone fluid is that all other DOT 3, 4 or 5.1 is heavier so it goes to the bottom and silicone fluid stays above it. In a typical brake system (Not the Greenbrier) the master cylinder is above the wheel cylinders or calipers so the new fluid displaces the old fluid right Dow to the bleeder. In the case of the new Wilwood calipers on the Cobra, I have bleeders top and bottom.

With the Greenbrier I forced air throughout the system to render it "dry". I then flushed it out with denatured alcohol, followed by more air. I the replaced the master cylinder, the steel brake lines and hoses. The only wet part not replaced were the wheel cylinders. New military grade silicone fluid while using a power bleeder and after a complete bleed, very firm brake pedal. We took the Greenbrier to Murphy, NC and took it up to 3100 feet altitude without any issues.

My concern was with long term use possibly causing corrosion but sure looks like nobody has run into that. That makes me happy!

64 Greenbrier
64 Spyder (needs restoration)
65 Corsa 140, restored
66 Corsa turbo, restoring now
66 Corsa 140 "RR" code coupe fully restored
67 Pontiac GTO restored
69 Corvette 427 convertible restored
2004 Caterham R400 (Lotus super7)my race car
2004 Porsche 996TT convertible
2015 Corvette Z06
1965 AC Cobra (Factory Five)

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Re: SILICONE BRAKE FLUID -GOOD OR BAD ?
Posted by: Frank DuVal ()
Date: May 15, 2017 03:19PM

I stated my results-which are positive.

Others repeated internet heard horrors. Not helping. Melb wants reports of use.

If I have a choice between a fluid that absorbs water out of the air so bad that the container says right on it NOT TO USE IF OPEN and a fluid that does not absorb water out of the air...guess which one I would use, oh that's right, I already answered that. DOT 5 for me.

I use DOT 5 in the "open" systems of the pre 60s and it still does not absorb moisture from the air, even after years in use. Why? Oh yes, it isn't hygroscopic.

BTW, wheel cylinder cups are designed to leak a tiny amount of fluid to keep them lubricated. That's why DOT 3 makes those white crystals on the metal WC cups long before an actual drop forms. Maybe people in low humidity areas do not see that.

As to DOT 5 contaminating shoes, well, I have not had a seal failure yet, so it is a non issue. And even if DOT 3 got on shoes they would get replaced anyway unless made from unobtainium. Of course in my frugal youth, lacquer thinner in a wheel cover, soak....dry....soak again.... Danger? What danger?eye popping smiley

And I do not have low brake pedal, or soft feel like I read on the internet.grinning smiley

Frank DuVal

Fredericksburg, VA

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Re: SILICONE BRAKE FLUID -GOOD OR BAD ?
Posted by: dolomitefan ()
Date: May 16, 2017 01:05AM

The main difficulty silicone for a road car is bleeding it through as it does like to bubble. I echo the thoughts of others on using a power bleeder, furiously pumping at the pedal will cause it to froth and you'll never get a good bleed. In fact this is why you wouldn't use in an ABS car.

I was working on part of my brakes last night and this thread has made me think more about the fluid I will use. I'm pretty sure I'll go for silicone. I will be fitting braided hoses though as they look nice and should keep the pedal a bit firmer.

It's interesting to hear so many people talk about DOT 3 fluid. In the UK we cannot get DOT 3 now, it's all DOT 4 or 5.1.

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Re: SILICONE BRAKE FLUID -GOOD OR BAD ?
Posted by: iceking888 ()
Date: May 17, 2017 04:17AM

I have had silicone in my vehicle since I bought it in 2009. The only issue I have had is the brake pedal is extremely hard to push, almost like you are stopping the car yourself thru the floor. Is that normal? Mine is an early model and I heard somewhere that you can swap out the original master cylinder with one that is used for turbos. Are they not the same and does that sound correct? If that's the case, its an easy fix.

Dante

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Re: SILICONE BRAKE FLUID -GOOD OR BAD ?
Posted by: Frank DuVal ()
Date: May 17, 2017 09:33AM

No, the metalic brake option (not turbo option) got the different brake master cylinder. But, they also used different size wheel cylinders. SO, not easy, and NOT a good suggestion!

Take all four wheels off and see if all 8 pistons move free when the brakes are applied (gently, since the drums are off).

Also, 60 & 61 use a completely different MC than the 62 to 66 cars. So what year early matters to your first thought.

Frank DuVal

Fredericksburg, VA

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Re: SILICONE BRAKE FLUID -GOOD OR BAD ?
Posted by: jjohnsonjo ()
Date: May 18, 2017 01:31PM

If you have long life brake linings the pedal will be hard. Its best to use FLAPS cheapos that have a softer and more grippy lining.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa

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Re: SILICONE BRAKE FLUID -GOOD OR BAD ?
Posted by: Melb-Mike ()
Date: May 18, 2017 02:01PM

I'm not a brake expert but I found no difference in my Greenbrier or Cobra with Pedal effort before and after using silicone. I use those two as an example since both use a manual master cylinder. The Cobra uses a 1995 Ford Mustang SVT aluminum master cylinder with a 15/16" bore. The Greenbrier uses Clark's twin master cylinder made of cast iron with an unknown bore size. My 69 Vette has power brakes with huge disc rotors & 4 piston calipers, and stops like an angry bull from any speed.

I would recommend anyone who uses silicone fluid to use a power bleeder and do the bleeding in two stages, 24 hours apart. That gives the fluid enough time to combine the little air bubbles into a bigger one that is easier to bleed off. I have a very firm pedal on all the silicone fluid cars.





Wrote:
-------------------------------------------------------
> I have had silicone in my vehicle since I bought
> it in 2009. The only issue I have had is the
> brake pedal is extremely hard to push, almost like
> you are stopping the car yourself thru the floor.
> Is that normal? Mine is an early model and I
> heard somewhere that you can swap out the original
> master cylinder with one that is used for turbos.
> Are they not the same and does that sound correct?
> If that's the case, its an easy fix.
>
> Dante

64 Greenbrier
64 Spyder (needs restoration)
65 Corsa 140, restored
66 Corsa turbo, restoring now
66 Corsa 140 "RR" code coupe fully restored
67 Pontiac GTO restored
69 Corvette 427 convertible restored
2004 Caterham R400 (Lotus super7)my race car
2004 Porsche 996TT convertible
2015 Corvette Z06
1965 AC Cobra (Factory Five)

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