A brake caliper that leaks fluid is a safety problem - it loses the hydraulic pressure that stops your car. Catching a leaking caliper early prevents a dangerous failure. Here are the signs and what to do.
Where a caliper leaks
A caliper typically leaks at the piston seal - when the piston seal or dust boot fails, fluid weeps past the piston - or at the bleeder screw or the hose fitting. Corrosion and age are the usual causes. The leak lets air in and fluid out, undermining braking.
The visible signs
Look for wet, shiny brake fluid on the caliper, the inside of the wheel, the pad, or the ground where you park; a greasy film on the inner tire edge is a classic clue - see brake fluid leak signs. Fluid on the pad also contaminates it, causing grabbing and noise.
How it feels
A leaking caliper causes a soft, low, or sinking brake pedal as the system loses pressure - see when a soft pedal is urgent - and a slowly dropping reservoir; see why is my reservoir low. You may also notice a pull toward the leaking side.
What to do
A confirmed caliper leak means do not drive it - fluid loss can cause sudden brake failure. Replace or rebuild the caliper - see rebuild vs replace - bleed the system, replace the contaminated pad, and refill with fresh fluid. Fit quality pads and fresh hardware.