The movement of the piston in the Infiniti Disc Brake Caliper is what the brake fluid pressure presses against so friction can be created by the pads and the rotors in the braking system. It is the disc brake caliper that transforms the hydraulic pressure to a mechanical action in the braking system on your Infiniti.
The disc brake caliper has a brake hose attached to it that supplies the pressurized hydraulic fluid to it. This fluid then pushes out on the piston in the caliper which forces the brake pads against the brake discs. This is how your Infinite is brought to a standstill. The only moving part of this braking component is the piston. To keep the pressurized hydraulic fluid in the disc brake caliper, there is a polymer seal around the end of the piston. This is the only part on the caliper that will fail requiring the entire Infiniti disc brake caliper to be in need of replacement.
The polymer seal in the disc brake caliper fails because it dries out and ruptures leaking the hydraulic fluid out of this otherwise closed loop system. When this condition occurs on your Infiniti, brake fluid will be covering the brake disc and there will be a puddle of fluid on the pavement below. The brake pedal will also feel soft and could all the way to the floor in the braking action by the driver. This is brake failure and it must be addressed.
The replacement of the disc brake caliper is similar to replacing the pads with the addition of replacing the caliper itself. Once in place the brake system on your Infiniti will have to be bled of air so your vehicle can return to an operation status.