dintavian

quick question, I want replace my left front brake caliper for my GT. Do i have to clamp down the brake fluid, so it doesn't leak out? Or should I just let all the brake fluid out.

Cdn Blue Coupe

all of the brakes.

For myself I use a small wood plug to slow the leakage until I re attach things. You won't want to damage the hose by pinching or bending it too sharply.

Shadowfax

Bleeding is easy and replacing the fluid in the entire system every few years is good for the life of the internal parts and reduces the chance of fluid boiling in heavy use applications like racing and spirited city driving

anytime that you break open the system (like replacing a caliper)you will need to bleed the wheel in question at least or the entire system at best.
Go for it

VW-Quantum-Man

This means it "likes" water, brake fluid will absorb moisture that is in the air. Hmmmmmm, that means if it is exposed to air for a long time it has a lot of water in it, actually like 1.5% which means internal corrosion to brake parts. Every three years I change my brake fluid, yes I said change the brake fluid, as part of my regular maintaince.