Can brake fluid break down ?

If it contains water, and before stuff starts to rust, you may encounter braking problems. The terminology varies according to who you ask, but you can get fade whereby the effort at the pedal increases dramatically compared to the braking effort at the wheels, because you've boiling water (steam) in the system, which expands . . . nasty. This can blow out seals, so I'm told.

If in doubt, get it changed immediately. A car that won't start is a pain, a car that won't stop is a menace.

its not so much of the fluid breaking down, but the dirt in the fluid.. when it turns from clear to black then its well past due to have it change.....

yes you RIGHT, but i just call it dirt(dirty looking fluid)... in my neighborhood as a kid many years ago if you told someone what it really was they would look at you like you were nuts.... and because they and me did not know we just called it dirty.....

yes, it can also become contaminated with water . if it is clear and clean, it is ok. if it is muddy brown,or milky it is time to change it

Falcoon opined . if it is clear and

Again.. just my opinion but... if it's as above it's time to change out your entire brake system.

Do it all at once or one piece at a time ......but if you put ONE new part in and the stuff was that bad.. good chance you'll change each part more than once.