Does anyone use DOT-5 silicone brake fluid in their C3's ? I'm installing new brakes & would upgrade if it's better, but I've heard conflicting info about it. Good- it doesn't collect moisture; bad- should only used for occasional driving, not everyday street cars......any experiences ?

 

I am using silicone fluid in one of my 68's since 1980. Not a single brake problem since then. Same master, same calipers!

 

put mine in a month ago. no problem bleeding the system which is what a lot of naysayers said would be a problem. Actually should be no problem driving the car more. Supposed to be better if it sits then regular fluid because it doesn't pick up water. Works fine for everyday driving so far.

 

Thanks for the good reports.....sounds like a worthwhile upgrade.

 

I was told (and believe) exactly the opposite. Silicone brake fluid is designed for race applications. Silicone fluid will withstand high heat and the fluid is changed after every race, For a car that is NOT a daily driver, the system will build up small amounts of condensation inside the lines over time and that is what causes the softer pedal. Since switching over DOT4 brake fluid I have a much better pedal. I did experience the softer pedal issue with the silicone fluid. I would power bleed the system and within a 6 month period I had a soft pedal again. My booster and MC were new. I was using silicone fluid for quite a few years and just thought that was the way the Corvette brakes were (bleed every 6 months). Since changing to DOT4 I have had a good pedal since and its about a year now and not have had to bleed the brakes. I am not a scientist but I think when the silicone fluid heats up then cools and sits for a period of time creates very small amounts of water in the line I think because of the high oxygen content in silicone. Again I am not a scientist but it is something like that.

 

??? Moisture with silicone fluid ? I thought "no moisture" was its claim to fame.....soft pedal after 6 months?....

 

Supposedly, silicone gives a mushy feel...I thought silicone was only used for trailer queens since it wouldn't hurt the paint if spilled on it.

http://www.afcoracing.com/tech_pages/fluid.shtml
http://www.belray.com/consumer/Q&A%20pages/q&abf.html

 

I have had silicone fluid in my 71 Chevelle for 12 yrs. Zero problems.Will change the Vette over soon.

 

using silicone, and pedal is hard as a rock

 

That's what I thought also. But it was explained to me very technically and do not remember 1/2 of it, but in the end it did make sence and the silicone fluid seems to be best in race applications where the fluid is changed on a regular basis. I am just going by what someone (who is very knowledgable and with LOTA race experience, road course that is) told me.

 

i put DOT-5 in my 69 last year when i replaced the brakes. not a bit of trouble with it yet. infact, the brakes are better on the car now then they have ever been.

 

I've had silicone in my 78 since 93 and it's been great. Dot 3 fluid has an affinity for moisture and therefore must be replaced annually for best results otherwise corrosion sets in over time. It's best used when fluid is changed regularly.

Silicone has an affinity for air and its therefore more difficult to get air out of the system that's why it's not recommended for power bleeding and the more aggressive forms of brake bleed maintainence. The mushy pedal results from air that has been allowed to remain in the system. Also, I believe it does not perform as well at higher altitudes.

I believe you heard the reverse of what your friend intended.

 

Silicone here. Rock hard pedal like a 15 year old boy in the girls locker room at shower time!!!!

 

Silicone is NOT a race fluid, DOT 4, super DOT4 and DOT5.1 are and they are all glycol based, they have high dry and wet boiling points.

Glycol based fluids are hygroscopic, meaning they absorb water from the athmosphere so opening the lid on your master or an air pumping caliper willd eteriorate the fluid rapidly. Silicone is non hygroscopic and this may sound like a bonus (plus it doesn't eat paint but is more compressible) however there's a big drawback especially if you have a system that's not super tight & leak free. Any moisture in the silicone will not be absorbed, lowering the boiling point, but worse...it sinks to the loest level as a blob of water, the calipers...causing rust there and well..a blob of much more compressible liquid than the brake fluid, result a mushy pedal and destroyed calipers. I refuse to run it. Another drawback used to be sealing problems, there was something wrong with the swelling agents,...this has most likley been "fixed" but it is something to think about if your seals start leaking.

 

I have used silicone fluid since 1998 when i bought Muskegon Brake's ss caliper, master cylinder, etc. kit. no brake problems since. and at times I use my 79 vette as my daily driver during the warm months. silicone fluid is not a high heat, racing type brake fluid however

 

that sounds about right. ive been using silicone for about 3 years on a mostly new brake system. no problems.

 

I've never had a problem I have run it for about 19 years. I like it also because it doesn't eat paint and that has nothing to do with a trailer queen. I do regularly seem to be taking the braking system apart for other reasons, not braking problems and seem to spill fluid.
It does not absorb water and like Twin Turbo said water droplets form in low spots causing rust.

 

I too use silicone fluid. I've used it in Fords, Chevys and even Harley Davidsons. In more than 20 years of use, I've never had a problem of any type. Bleeding brakes needs to be a bit more deliberate as the silicone aerates and retains bubbles much longer than hydraulic fluid.

I find it perfect for occasional use vehicles and have let a number of mine sit for more than a year with a strong hard pedal as a reward. Silicone does not attract moisture, resists corrosion and if you spill it on your paint… just rub it in!

But more seriously, there is no reason why it can't be used in everyday vehicles with the possible exception of some ABS equipped vehicles. The Marine Corps (and I assume the Army) went to silicone brake fluid more than 20 years ago to reduce maintenance, in particular on vehicles and trailers that sat for extended periods of time.

Silicone fluid is not recommended for racing applications because it will expand when heated. In a closed system this can result in the brakes being increasingly applied which can lead to lock up. Having said that, I autocrossed my 1973 for more than 3 years with silicone fluid in it, with absolutely no adverse effects.

Until something more suited to my purposes comes along, I will continue to use it in everything but my racing vehicles.

GUSTO

 

i converted to dot 5 when i replaced my calipers...

1. it will not eat paint. DUDE, its a good thing i switched because i had brake fluid ALL OVER that car by the time i was done. i knew it wouldn’t hurt so i probably wasn’t that careful.

2. it may bubble up or fizz on you if you pump the pedal too aggressively before you have an air tight system. What I am suggesting is don’t do what I first did and use the old “pump pump pump … ok hold it!” trick. If you do, don’t be real crazy about it or you may just be making bubbles…

Oh, the stuff is expensive too. I used just over 2 quarts. Yes I spilled a little here and there. However, I also got a strainer and strained it back into the system. I think it was like $20 a quart.

 

Expensive? Try buying a bottle of the stuff when it's got "Harley Davidson" written on it!
I've been using silicon brake fluid in my bike for somewhere around 20 years & have NEVER had any sort of problem with it. The calipers are cast iron, without stainless sleeves, as is the master cylinder. Pedal/lever feel is a lot firmer than it was with glycol based fluids. Last time I pulled the system apart (to change an aeroquip hose that had frayed) there was no sign of any corrosion inside - it looked new. This last week I've spent hours & hours getting a master cylinder from the same type of bike, of the same age, apart. It's been run on Dot3 fluid which has been regularly changed (so the owner claims & the condition of the fluid tends to support the claim). The corrosion inside is bad, bad enough for me to refuse to rebuild it without replacing the cylinder.
Heat problems? I've ridden in the Pyrenees (& the Alps) with pillion & luggage (ie a lot of weight) & the brake discs (rotors) turned blue due to the heat generated (they've never done that before or since). The discs were so hot that the wheel rims themselves were hot to the touch from the heat conducted to them. The brakes still worked under thes heat conditions (& they were being used a lot).
The only problem with silicon fluid I've had is when bleeding. My front brake is effectively a vertical run of aeroquip hose & it literally bleeds itself. The rear, just like a car, has a horizontal run that has curves & bits that can trap air. You need to bleed with very slow, steady strokes (no jokes about teenagers in showers ). I've got transparent resorvoirs on the master cylinders & can watch the air bubbles coming up. If you pump the pedal the bubbles break up into smaller ones, if you vigorously pump it then the bubbles are so small that it looks like mist coming up through the fluid. As the bubbles are so small they don't rise through the fluid very quickly & 5 mins later there's still a line of "mist" in the resorvoir. Pumping the lever again just sucks all the miniscule bubbles back down into the master cylinder & brake lines. It takes a long, long time for those little bubbles to rise, or combine, so take it real easy when bleeding, otherwise you'll never get the air out.