Silicone Brake Fluid

[urpu36]

Thoughts?? I have been using it for over 20 years, maybe 30 years. Three reasons, doesn't eat paint, doesn't eat paint, and it doesn't eat paint. My experience is 99% Hot Rods, Street Rods, Muscle Cars. With all the aftermarket stuff there are always leaks and I have seen so much paint damage cause by DOT3-4 fluid. Also cars that sit a lot get crusty and leak after a while with DOT3-4. Silicone can sit for years. A lot of work to convert over because the system has to be completely cleaned of the DOT3-4. The spongy pedal I have heard about over the years can be eliminated by putting pressure on the pedal and cracking the bleeders after a few days, weeks, months, years or anytime the car is on a rack. The pedal is soft because of micro bubbles in the fluid that take a long time to work their way out. The bubbles either go out the master or get caught in the caliper or wheel cylinders after driving. Good for road racing, don't know, don't care. I don't road race. There was high hopes for the fluid when first developed but didn't take over like was thought. Nice purple color.

[FreeBug]

My only thoughts: it isn't hydrophilic, so it doesn't absorb moisture from the air -or from your brake system. Water will settle, if any gets in, and create small but deep rust holes.

Only really used it on collector cars which see few miles, and very little weather. No long-term experience with it in a daily driver.

[kreemoweet]

I put that stuff in my daily-driven bus 15 or more years ago. I just drained the old DOT-3/4 fluid out first, no special flushing. I think I also
replaced most of the metal brake lines at the same time. No problems at all. No soft pedal. Not a sign of rust/corrosion/water anywhere in the
brake system when I've had it open from time to time over the years (totally unlike any of the vehicles I've had using standard fluid).
I'm currently working on my second quart of DOT-5 fluid, so the high initial cost just doesn't signify.
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[KTPhil]

Many, many threads on this, such as this one:

https://www.thesamba.com/vw/forum/viewtopic.php?t=578728

[slalombuggy]

I use it in al my VWs and haven't had a problem, All my cars get completely new brake systems including stainless hard and soft lines. I like it because my cars sit for 6 months in the winter so no absorbing moisture is a big plus. I also race so having a very high boiling point is a good thing also. The fact that it doesn't destroy paint is a big bonus.

brad

[KTPhil]

It's long past time I should flush out my DOT5 that I put in about 7 years ago. My local climate rarely hits the dew point and so I get no condensation, but regardless, it's time. Still works great, though: hard pedal, no leaks, good feel.

[Stocknazi]

[modok]

Haven't had a problem with it since I put it in 15 years ago. Daily driver for 10 years.

Probably due for a rebuild.

I've changed around the drums and shoes a few times but not touched the hydraulics.
As I said in the other thread I did need to add stronger return springs, tho....the details of that now I have forgotten.

[vamram]

Do you have to replace the hard line of switching to DOT 5 or can you just flush it out with something else? And do you have to replace wheel cylinders and calipers?
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[kreemoweet]

[modok]

I replaced everything except the the hard lines, and blew those out.

[vamram]

What about the issue I've been reading elsewhere that water pools at the lowest point of brake systems using DOT 5, causing corrosion in those areas, because, since DOT 5 is not hydroscopic, it doesn't mix w/the water, which "can lead to boiling in heavy braking" scenarios and a soft pedal..? Or that the pooling water can freeze in cold weather?
_________________
Eventually, "we are what we pretend to be.’”
Give peace a chance - Stop Russian-Soviet Aggression!!

'74 Super 9/16 - present, in refurb process.
'73 Super - 6/18 - Present - Daily Driver!
'75 Super Le Grande...waiting it's turn in line behind '74.
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Save the Supers!!

[kreemoweet]

[modok]

are you storing it in a greenhouse?

Most classic cars live in warm dry garages, or in parts of the country with low humidity.

Or they will rust out in ten years probably.
But it could be a fun ten years so ok cool, and don't worry about the brake fluid either, flip a coin, nothing is forever.

Most people used dot5 because it doesn't eat paint.

[kreemoweet]

[modok]

WOW, well there you go.

[oprn]

[raygreenwood]

[slalombuggy]

I did a complete flush of my brake system last year. I put DOT5 in it in 2009. I let it sit over night in a glass jar. Inspected it the next day. Saw no signs of water, rubber, rust or other contaminants.

[Rickf1985]

I can tell you from working on antique military vehicles for 40 years that silicone fluid does get moisture in it and that moisture will migrate to the lowest point in the system, the wheel cylinders. Flushing will not remove the water since it is laying on the bottom of the wheel cylinder and the fresh fluid is coming in the top and the old fluid is going out the bleeder, also on top. Military vehicles use nothing but DOT 5 fluid. They both have their good and bad points. 3,4,5.1 will all work fantastic as pain removers. They also are hygroscopic and absorb moisture. That said a flush every year or so completely eliminates that moisture since it is contained in the fluid. DOT5 will not "Absorb" moisture since it is not hygroscopic but, the system still has to be able to breath so as fluid level drops (disc brakes and unadjusted brakes) the diaphragm in the master cylinder can also drop and the master does not develop a vacuum. Just flushing DOT 5 will not remove the moisture trapped in the bottoms of the wheel cylinders but you also will probably not need to do it as often. But to completely clean out a DOT 5 system you need to pop open the wheel cylinders and wipe them out.
To do a conversion in either direction you need to drain the system, open the wheel cylinders so they are also empty, put that all back together and fil the master cylinder with you new fluid before hooking up the lines to the wheel cylinders. Let the new fluid run out the ends of the open lines for a bit to clear out any old fluid left in them and then plug them back into the wheel cylinders and bleed as normal. You are done. There is no need to worry about the very small amount of leftover fluid that is sticking to the insides of the lines, this will not be enough to cause a problem. It is when someone does not know a vehicle has 5 in it and refills the master with 3. Down the road you system ends up with a gooey gel in it. I have repaired a few of those.