The pressure being generated by the Nissan brake master cylinder is the source for the hydraulic power that makes it possible for the modern braking systems to operate. This braking component is located in the engine compartment and is connected to the brake pedal by a lever. Inside of all brake master cylinders is a piston. The seals on this piston can be breached by the hydraulic fluid which can cause this brake component to fail. This is a rare occurrence, but can happen over the lifetime of your Nissan if it is driven in excess of 100,000 miles. The failing of the brake master cylinder on your Nissan may not necessarily display any external problems. The symptom of this seal being breeched is manifested in the brake pedal when pressure is being applied. A driver will feel the brake pedal continuing to move towards the floor of the passenger compartment with no additional braking force being applied into stopping the vehicle. This is the same symptom as a leak in a brake line or hose, but this time there will be no puddle of brake fluid on the pavement below the vehicle. Since the Nissan brake master cylinder is the pressure generating device for your braking system, its failure will cause the entire system to fail in a very short allotment of time. This will require the brake master cylinder to be replaced immediately or the Nissan vehicle will not be safe to operate on the road. The brake master cylinder can be replaced in less than an hour but the final step will require two people. This step is the bleeding of the brake system so all of the trapped air in the brake lines and hoses can be removed.