Bleeding master cylinder in the car
The lines should be completely filed with fluid (along with the wheel cylinders, master and calipers) normally I would think of condensation as moisture that came out of solution from the air because of a drop in temperature. If the system is properly bled (no air bubbles in a system - a condition that would have its own issues) then there is nowhere for any moisture to be in the system at all, until something fails. I'm not a mechanical or chemical engineer, but I would hate for folks to not take an excellent remedy for an old problem if indeed there are no issues with the DOT 5. Ehrenberg, the tech editor at Mopar Action has been recommending DOT 5 for many years. I hope someone with some real qualifications can give us more info.
The system is not going to be completely full of fluid, because for brakes to work, fluid leaves the master cylinder, when the brake is pushed, filling the wheel cylinders, and calipers full of fluid, which stops the car.
When the brake petal is released, the fluid travels back to the master cylinder. The wheel cylinders, and calipers will not be full of fluid and the car moves.
A cold system, when heat is introduced, will sweat causing condensation.
Its simple physics.
Why will a good looking brake line, actually break, because it rots from the inside out.
DOT 3 or 5 will work, if you have replaced every component, at our age you will not have to worry about it.
Real qualifications, I am a degreed engineer, and have worked in industry for over 30 years designing aircraft.
