[PLAY400]

I noticed several references to this in the winterizing your car post. what is it and what are the advantages of using silicon brake fluid?

[PLAY400]

I noticed several references to this in the winterizing your car post. what is it and what are the advantages of using silicon brake fluid?

[72LeMConvt]

The main advantage to silicone brake fluid (a.k.a. DOT-5 fluid) is that it DOES NOT absorb water the way conventional brake fluid does. Normal brake fluid will absorb moisture right from the air (hygroscopic), so that every few years, you should bleed your brakes. Most of us don't do this, so the fluid degenerates and calipers and wheel cylinders tend to sludge up over time.

A second benefit of silicone brake fluid is that it usually has a higher boiling point than conventional brake fluid, making it more suitable for high temp. applications like road racing or mountain driving.

Silicone brake fluid is absolutely NOT compatible with conventional brake fluid, so a very thorough flush or cleaning must be performed prior to making the switch - calipers, master cylinder, wheel cylinders, lines, hoses, etc.

I think that about summarizes it. Good Luck,

Kirk

[455Dave]

72LeMConvt is right, they are not compatible. The previous owner of one of my cars failed to flush the calipers on a swap from Dot 3 to Dot 5 and it created a slimy goo that ate seals and bores like crazy.

Dave

[Herb Hagan]

Another inportant benifit to dot5, it will not eat paint like conventional fluids

[critter]

There is a downside. Price. The silicon fluid is expensive. That said, I run it in my car because of all the benefits it provides.

[Skip Fix]

Some say silicon can have a spongy pedal feel but always felt normal to me in my 78.

[PLAY400]

How does one go about flushing the brake system? Would it be acceptable to use my vaccumn/brake bleeder pump to draw out all the old fluid out , refill with DOT-5, then keep drawing the fluid out until it comes out clean. Or should I purge the lines then disassemble and clean all the wheel cylinders and master cylinder.

[critter]

Since mine was put in post restoration and all my hardware was new, I did'nt have to purge. I'd suggest some type of mineral spirits to flush it out before adding the silicon.

[72LeMConvt]

I'd definitely disassemble & clean the calipers, wheel cylinders & master cylinder. As for the lines, I, too, was replacing lines & didn't have to worry about it.

But, IMO, you should use compressed air along with a solvent that cuts brake fluid. I'm thinking that mineral spirits doesn't do that, but am probably wrong ??

Kirk

[critter]

What about alcohol? That would clean it and not leave a residue. Just a thought.

[72LeMConvt]

Yea, that'd probably be my choice, too.

[Skip Fix]

I just pressure bled the front calipers and rear lines when adding rear discs, new rear calipers so they wer fresh. That was over 10 years ago and still works great.

[72LeMConvt]

Wow, and no troubles since??

I did that to a motorcycle I owned once and after a time the brake began to drag badly. I disassembled the caliper and found a hard-ish crystallized substance. Found it in the master cylinder, too. I've since been told that's what happens when you mix conventional with silicone fluid.

Maybe my experience was a fluke thing (and hence the foundation for all my above statements)......

K

[Joel Koontz]

I use Silicon Fluid in my GTO and in my motorcycle. I had all new parts (therefore no DOT 3/4 fluid) when I converted the car. On my bike I just drained out all of the DOT 3/4 fluid that I could and then bled the lines several time with Silicone Fluid (does not hold near as much as the car). The same Silicone Fluid has been in the bike for over ten years without any problems.

If I was going to try retro-fitting a car with DOT 3/4 in the system I think I would try to drain/bleed it as much as possible then try using the brake cleaner that comes in aerosol cans to flush the system. It evaporates quick but a couple of cans should be enough to flush the system. I have never heard of anyone using it but it apparently is OK to use on brake components and should clean thoroughly.

If anyone has tried, or tries, using the aerosol brake cleaner to flush the system, please E-Mail me to let me know how it works.

Joel

[Jim Roberts]

DOT3 fluid is water soluble! DOT4, Castrol LMA (Low Moisture Attraction), also water soluble.

I usually flush lines with water, blow dry with compressed air, and then hit with brake cleaner & air again for good measure. Have done it this way many times when converting to silicon fluid. Did this with the metering & proportioning valves on my Tempest and with the long line from front to rear which looked nearly impossible to replace. As long as you are able to blow the water out with compressed air immediately, flush with a hose adapted to the brake fitting until the water comes out clear, blow out, then use brake cleaner and air again. The NAPA brand is excellent and not too costly. It is advisable to replace/rebuild all calipers, wheel & master cylinders, and replace the flex lines since brake cleaner can attack rubber.

One other advantage is that the seals stay lubricated much better with silicon fluid. Disadvantage is that it holds air bubbles longer so fill the master and pump the pedal slowly when bleeding. I used a vacuum bleeder on the Tempest and the manual method at the resto shop I used to work in. Never had a problem either way.

Spongy brakes with Si fluid??? Notta chance unless there are other problems like bad flex-lines, seals, or air in the system.

[ron cozzo]

When I rebuilt my brake system I used synthetic brake fluid, Valvoline SynPower High Performance Synthetic Brake Fluid. Beacause I hadn't replaced the hard lines or master cylinder I didn't want to mix with silicon. Advantage: Low moisture, compatible with standard brake fluid. Disadvantage: Eats paint.