The mechanical motion of the Mitsubishi disc brake caliper is generated by the hydraulic pressure sent to it by the master cylinder when the brake pedal is depressed. This can be seen by the action of the pads being applied forcefully against the brake rotors that will stop your vehicle. There is a disc brake caliper on every wheel assembly that has the disc brakes on your Mitsubishi. The mechanical motion of this braking component actually comes from the piston on the inside of the caliper. The hydraulic pressure being applied to this piston forces it outward, and it pushes the brake pads against the disc surface. The friction created from this reaction stops the vehicle's motion. Every disc brake caliper has only metal components to them except for the seal around the piston which holds back the brake fluid. It is this polymer seal that tends to break or crack over time. This allows the brake fluid to leak out, and impairs the stopping ability of your Mitsubishi. The driver may notice a soft brake pedal and/or a puddle of fluid on the pavement near the wheel assembly where the leak occurs. The only cure for this situation is the replacement of the Mitsubishi disc brake caliper. This can be a new or rebuilt part. This procedure consists of removing the wheel and disconnecting the brake hose from the disc brake caliper, then the entire caliper itself. When the new component is in place, the disc brake caliper then has to be bled of the air that is trapped inside of it. Once completed then the wheel can be placed back on your Mitsubishi and it should be road ready again.