<VV> was synthetic oil, now silicone brake fluid

[Bill Elliott]

>OK, if there is air suspended in the silicon fluid with moisture in it why 
>does the moisture not settle out to the bottom of the DOT 5 bottle?  

If it sat undisturbed long enough there might be. The moisture is trapped in the air suspended in the 
fluid. Heat is likely also a factor.

Remember 
>water will not mix with silicon fluid.  If there are microscopic pores in soft 
>brakes hoses the fluid would leak out when you press real hard on the brake 
>pedal. 

Nope, different sizes. Air can pass through where liquids cannot.

 Also, air is not drawn into the reservoir as the pads or shoes wear 
>because there is an accordion boot under the master cylinder cover that expands if 
>the level drops and keeps air from being drawn in.

You are right that the boot minimizes air being drawn in, but does not prevent it.

  The amount of time that 
>the cover is off of the master cylinder to check the fluid level is minuscule 
>and is not long enough to allow moisture in, unless you check the fluid out in 
>the rain.  Face it, how many times a year do you check the fluid level? 

Wrong. If this _were_ true, how would moisture get into gylcol-based systems? _Any_ exposure to air 
lets moisture in. 


 With 
>silicone fluid in a sound brake system there is no loss from evaporation in the 
>life of the system.  With disk brakes as the pads wear down the fluid level 
>does drop slightly but you should not add fluid because when you replace the 
>pads the fluid level will be pushed back to its original level and if you added 
>fluid the master cylinder would be over filled and malfunction.

Agreed. 


>As far as there being a problem with hot brakes under hard use like racing, 
>my son and I both autocross with silicon fluid and the brakes get so hot the 
>smell and smoke with no problems. 

Autocross is very different than racing OR even hard street use. But I'm glad you're not having any 
problems with it. Depending on your shoes, getting them hot enough to smoke _may_ not be heating up 
the wheel cylinders enough to cause you a problem.

 NASCAR racers don't use silicon because their 
>brakes actually get red hot for an extended time and that is another matter.  
>They also don't use DOT 3 because of the extreme heat.


I wouldn't use DOT 3 either. In my initial post I recommended fully synthetic Valvoline Synpower DOT 
5.1. This is the cheapest option in the family of fluids they DO use.  Otherwise I use Castrol GT/LMA 
(DOT 4).

Look, I am NOT an expert in brakes and/or brake fluids. I HAVE seen silicone systems FAIL in Corvairs 
under heavy use. You can reason it out all you want to, but that doesn't change the fact that while many 
folks seem to use it with no issues whatsoever, some folks have experienced very serious problems... 
and typically not even with older fluid.

Maybe they didn't bleed carefully enough. Maybe they shook the bottle too much and had excess air 
suspended. Maybe they didn't have their brakes properly adjusted. And maybe they used older, open 
fluid. Maybe they used a more aggressive shoe that created more heat before the shoes itself exhibited 
fade. 

But in any case, the added compressability of the silicone fluids resulted in brake failure during hard use. 
And that just doesn't happen (at least not in street use) with glycol-based fluids even if you do a lot of 
this stuff wrong.

Again, if it's working for you, great! If you are still concerned in the least, then google the info yourself 
and see what the experts DO say and why. I'm sure you'll find some experts on both sides.  If you're 
NOT concerned, then why keep trying to argue why I'm wrong? I am only stating my observations and 
why it happened according to the experts.

Bill