Worn caliper pistons, broken delivery lines.
Check the brake fluid reservoir, it may be low on brake fluid indicating it is time to have the brakes inspected.
Could be a few causes of that symptom, but most likely air in the brake lines or moisture in the brake fluid. Start by replacing the brake fluid in the reservoir and bleeding the brakes.
try bleeding the brakes or checking the fluid
have you checked your brake fluid??
Your brake fluid is how the brake system converts mechanical force of your foot on the brake pedal, into hydraulic force that applies your brakes. Without fluid, your hydraulic brakes will not function.
Air in the brake system- Brake system needs to be bleed and fluid needs to be added while you are doing that.
Caliber is sticking. More than likely the brake fluid is contaminated with moisture which has caused the brake caliber to rust. I would recommend you have your brakes inspected and replace any caliber that is sticking. Also have the brake fluid changed immediately.
Bad fluid in master cylinder,flush system,bleed brakes
In the brakes.
the biggest thing that causes brake fluid to turn "black" is high copper content. This is the result of your brake line deteriorating from the inside. when it is black you really should change it. the copper will start wearing out your rubber seals in your brake system, eventually resulting in............................. NO brakes!!!!
Probable causes: Low or no fluid in reservoir; Worn brake pads/shoes; Air in brake lines; Leaking brake line.
Brake Fluid.