Sorry I forgot to look at this thread.
“Ideally, silicone fluid (DOT 5) should be used only to fill non-ABS systems that have not been previously filled with glycol based fluid (DOT 4). Any system that has used glycol based fluid will contain moisture; glycol fluid disperses the moisture throughout the system and contains corrosion inhibitors. Silicone fluid does not allow moisture to enter the system, but does not disperse any that is already there either."
You get a pocket of water you can't bleed out without flushing the whole system and putting DOT 4 back in.
About the DOT system in general. DOT 5 is not better than DOT 4. It’s a different fluid with different properties designed to work in a DOT 5 system. You won’t have any gains from using it and potentially it can hurt your whole system by corroding components or things like that I think but mainly moisture issues. The best upgrade to fluid is to use fresh fluid from a new sealed container. Brake fluid soaks up moisture from the air as soon as it’s opened and relatively fast. That decreases the density and can give you swishy brakes. They do sell fluid that is compatible with multiple systems but I stay away from any universal fluid. Just like I wouldn’t use universal coolant on an Audi or VW that uses G4 (pink). Some say you can but I think that that they make things for a reason. A lot of time and money goes into the design of fluid systems so it’s best to abide by the standard.
Who knows you may never have a problem but by the way it sounds you do have a problem and if you’re going to flush the whole system anyway I would refill with DOT 4.
All this aside the boiling point of DOT4 is 446 degrees F. If you can bring that to boil you are my hero.
Look here is you want more info.
http://en.wikipedia.org/wiki/Brake_fluid