Brake hoses most often leak in one of two places: a crack in the rubber, or right at the crimped metal end fitting. A crimp leak is easy to miss and genuinely dangerous. Here is what causes it and why you cannot ignore it.
What the crimp is
A flexible brake hose has metal end fittings crimped onto the rubber to connect it to the hard line and the caliper - see brake lines vs hoses. That crimp is a high-stress joint: it seals high-pressure fluid while the hose flexes with the suspension thousands of times. Over years, corrosion and fatigue can let it seep.
Why crimp leaks happen
Age and vibration loosen the seal; road salt corrodes the metal fitting from outside; and internal rubber degradation lets fluid weep past the crimp. Because it is a slow seep rather than a spray, a crimp leak often shows up as a damp, greasy film around the fitting and a slowly dropping reservoir - see brake fluid leak signs.
How to spot it
Look for wetness, a shiny fluid film, or crusty residue right where the rubber hose meets the metal end. Compare both sides. A soft or sinking pedal alongside a damp crimp confirms it - see when a soft pedal is urgent. Wipe it clean and recheck after driving to confirm fresh weeping.
Why it is urgent
A crimp seep can progress to a sudden failure, losing braking at that corner or that circuit - see brake hose replacement. Any confirmed hose leak means do not drive until it is replaced and the system is bled. Replace worn pads and hardware at the same time if due.