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A friend maintains a private collection of Corvettes and has noticed that several of the cars have crystal clear brake fluid while others have a more cloudy appearance, the clear ones could simply be the result of a well restored brake system while the others may be contaminated by impurities, (rust) Does anyone know of a method to determine if a car has silicone brake fluid or not. I attempted to search the archives with no success. Thank all for any assistance as always.
Get a small paper cup. Draw a little fluid out of your MC. Mix some regular brake fluid with it. Let it set if it mixes and doesn`t separate you have regular fluid.
Here's another trick. Conventioal glycol based fluid is miscible with water , silicone is not. The glycol based fluid absorbs moisture which slowly corrodes the iron in the system resulting in darkening of the fluid. Modern hydraulic systems beginning with aircraft control systems in World War II use mineral oil based hydraulic fluid with synthetic rubber seals. When hydraulic brakes first appeared on cars about 1920 the natural rubber based seals had no resistance to mineral oil so they had to come up with something else. Glycol was the best available material at the time, and we are left with this unfortunate legacy. Conventional brake fluid must be changed periodically to prevent corrosion from destroying the brake system from within. When guys first started having problems with Corvette disk brakes back in the '70s, it cost about as much to rebuilt the brakes as rebuild an engine. It's virtually impossible to change to silicone fluid by convention flushing techniques, so only change to silicone if you completely start from scratch with a new, dry system.
A little off of the topic, but regular brake fluid, DOT 3 or 4, will absorb moisture as a result of normal aging. It tends to turn the fluid pale tan or light brown. This can occur in just a few short months. Tell your friend not to worry about this. This is one of the reasons that I bleed my brake fluid yearly in my 66. It has stainless steel sleeved calipers but not silicone brake fluid.
There are many excellent responses here regarding means of differentiating silicone from glycol brake fluids. I've always used the one suggested by Wayne Womble; silicone is not miscible with water and glycol is. I put a little in a clear glass vial with water and shake. If it phase-seperates, it's silicone; if it mixes, its glycol.
By the way, silicone DOT 5 brake fluid is colored purple. However, the purple is a dye which rapidly degrades to a YELLOW color in service. So, you can't assume that if the fluid color is not purple then the fluid is not silicone.
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