I wonder if it's moisture. Silicone fluid is non-hygroscopic, so the moisture would settle out, and might make some kind of sludge like that.

I'd take glass jar with some new fluid and add a small amount of water and let it sit for a while.
David

 

David,
Thanks. Maybe that is it but I keep the car and the fluild indoors, and it has never been in the rain, and I'm super careful about contaminants. But I will try this and see what happens. I posted this to see if anyone else has had a similar experience. I've had in in my Corvetee and WWII 3/4 ton Dodge and never experienced this, but I have to check them now too.

 

I've been using silicone fluid for 15 years and have never seen this.

 

FYI update:
This past weekend I was at my friends garage and he had a gallon jug of mil spec silicone with about 6 oz in the bottom. This is the same purple dot 5 I was using. And sure enough there was a table spoon worth of that orange crystal in the bottom of that jug. So that makes 3 different bottles I have seen this in. His fluid was also aged about 7 or 8 years as it was marked tested 2001. Just for your info. I also am doing tests by mixing the Dot 5 with :water, alcohol, dot 3 and oil to see if I can replicate this.
I asked some mechanics in the National Guard if they have ever come across this and they said no.

 

I am assuming that you are using silicone fluid because of the fact that conventional brake fluid can damage paint if spilled. I thought about that when I was building my car untill I did some research and found out how much silicone brake fluid sucks.. So, I was just careful not to spill the stuff on my paint and kept a damp rag around when messing with the stuff in case of a spill.Take everything apart, flush with real brake fluid till you are blue in the face and go. Why are you using silicone brake fluid? Not getting non-silicone on your paint is not that hard to do. Even if you spill a little a quick rinse with water will take care of it.

 

Actually it had nothing to do with getting DOT 3 on paint. I switched to DOT 5 back in the 1980's because I was tired and frustrated of replacing wheel cylinders in my '73 Corvette and a '69 Ford pickup with a plow, neither of which were driven more than 200-300 miles a year. The truck is long gone, but I still have the Corvette, and I have never had a leak or replaced a Wheel cylinder or Master since. Honestly every spring it was one or 2 of the 16 wheel cylinders leaking. Silicone DOT 5 stopped the internal rusting. Also at the time DOT 5 had a higher boiling point, and yeah it didn't cause paint to lift(not only on the body, but on the backing plates and wheels when they went bad.) I used Silicone on an awlful lot of cars I have owned, mainly Military trucks and never had a problem until this year with this crystalization. I'd be using it in my daily drivers if they didn't have ABS. On cars that sit more than they are driven, Silicone was a godsend. Just ask Uncle Sam, the Military uses it in all those trucks, that tend to sit for weeks and months and years with out ever moving. I think at one time the USPS was using it exclusively. Anyway thanks for reading and I welcome your comments, I just have had a couple of maintenance free decades with all of my brake systems, and was enjoying it.

 

Uncle Sam flushes em and replaces the fluid annually, whether they sit or not.

 

Ok, I understand now. However, if the issue is rust in the lines and other components due to the water absorbed by the fluid, wouldn't changing out the fluid reduce this effect? I was under the impression that the silicone stuff was far inferior in performance.

 

I bet the provider is skinping on the recipe, That fluid sitting for 8 years should not mater as long as it was closed up. I say this because almost every car goes that long without breaking into hydrolics for that long. I have never seen it in off the shelf auto parts fluid anyway. I bet they get the watered down version for 100 bucks a pint. You probably got it again due to residue left over. I would replace the master wheel cld then preasure bleed it real real well. Then flush it again in a couple of weeks. Prop valve would only make sence to replace aswell. Sorry no easy out here.

 

I have a small car collection that seldom gets driven, including some corvettes.. I experienced the same problem as skiski mentioned (leaks, bad cylinders, etc) until beginning to switch to silicone fluid 20 years ago. Since then, when I do the brakes on a car, they *STAY* done.. no more problems. I have a '69 Corvette that was the first I converted 20 yrs ago, and the brakes are always great... I'm so confident in it, that I have not even checked the MC in many years, so I guess after reading these 'orange crystal posts', I should take a look..

 

just a tip, silicone is fine for collections, light driven cars but is dangerous and in a lot of cases banned from road course use. (I know a few of the clubs I run HPDE's with won't let you on the track if it's in your car- they tech for it.) Terrible stuff if you drive the cars hard. great for trailer cars or ones that sit a long time and then just do pleasure use.

 

I have been using silicone brake fluid in my camaro for about 13 years. Never had any problems and just removed the brakes to put bear brakes on and the fluid was nice and clean. The fluid was still a purple / blue color. This is a weekend driven car also.

 

yes, but no offense intended, but a pro street car typically does not see the brake abuse that say a pro-touring or even daily driven car might- it's just meant as a word of caution for anyone doing performance driving not to use silicone.