MSG Equipment summarises the symptoms and causes of caliper failure and the basic steps of dismantling and inspecting a caliper with a repair kit.
Most modern cars use disc brakes, with the caliper at the heart of the system. MSG Equipment’s article lists longer stopping distances, the car pulling during braking and unusual noises as typical signs of a faulty caliper.
Common causes include worn guide pins, damaged piston boots, corrosion from dirt trapped behind the boot and leaking piston seals. Many of these faults can be fixed more cheaply with a repair kit than by replacing the whole unit.
The article walks through basic steps: removing the wheel, checking pad wear, clamping the brake hose to avoid fluid loss and inspecting the piston for dirt and damage. If damage is found, the caliper should be rebuilt.