The Toyota power steering lines and hoses are part of the closed loop hydraulic system that makes it easy for the driver to maneuver their vehicle. If there is even a small breach in this system, it will not be capable of functioning as expected. The power steering hoses are manufactured to last of many years on your Toyota, but the polymer component of the hose will have a breach created in it over time requiring it to be necessary for its replacement. The walls of the hose are thick and reinforced with fibers, but the hydraulic fluid is pressurized to a very high level. This places a strain on the power steering line which is why a breach will eventually occur. Once a breach occurs in the either the Toyota power steering hose, hydraulic fluid will leak out and be replaced by air. When the system is being operated, this breach in the power steering line or hose can be identified easily be an inspector of the Toyota looking for a small fountain type of event emanating from the breach. The driver of the Toyota will notice the pressure they will have to exert on the steering wheel will be increased when this breach in the power steering hose happens. This increase is due to the reduced ability of the power steering system to transfer the required level of pressure from the power steering pump to the steering box because of the air that is now present in the system. The air is being compressed and condensed rather than maintaining pressure. This is why hydraulic fluid is the medium used in this system, because it is impossible to compress liquid as opposed to gas.