Why it is important to be sure that there is no air in the steering gear system?

All cars with Power Steering use a hydraulic system. This means that is uses oil compressed by a pump to push a cylinder, or gear box mechanism to turn the rack on the car. If there is air in said system, the air will compress instead of the oil being pushed, thus resulting a delayed, or soft steering situation It can be dangerous to drive a car with air in the power steering pump assembly. It may fail and cause the car to steer out of control.