General information
Brake fluid is hygroscopic, which means it absorbs moisture from the ambient air and must always be stored in air tight containers.
An increase in the water content in the brake fluid causes its boiling point to drop. A reduced boiling point can cause vapor bubbles to develop as the fluid heats up under intense braking. In this condition the brake is likely to fail completely.
Brake fluid will take on a darker color after some time. This discoloration is the result of chemical reactions, and is NOT an indication of the fluid losing its properties. The effect appears after a relatively short time (few weeks), on vehicles installed with ABS even faster.
Avoid any contact of rubber components of the brake system (sleeves, sealing rings) with mineral oil, oils, greases and cleaning solvents!
Even very small amounts of the above substances will transform structure and dimension of a sealing ring or sleeve enough to adversely affect brake function. The effects of a polluted brake system will not be noticed for several months until they have caused damage that requires extensive servicing, especially on vehicles installed with ABS.
A = Sleeve - original size
B = Sleeve - swollen as a result of contact with mineral oil
The above mentioned points require special rules for handling:
Always keep containers holding brake fluid tightly shut. Only this will safely keep oil, dirt or detergents as well as moisture in the atmosphere from entering and polluting the brake fluid.
Take extra care to store containers holding brake fluid separate from containers holding oil (including hydraulic fluid) or liquid detergents. This will prevent any chance of accidentally mixing these fluids or even filling the brake system with the wrong fluid.