Most power assist steering systems function by using hydraulic fluid under pressure to multiply the force applied by the driver to the steering wheel. To accomplish this, high pressure hydraulic hoses connect the power steering pump (mounted on the engine) to the steering gear (mounted on the chassis.)
When the steering system shows signs of leakage or inconsistent power assist, it is wise to inspect the power steering lines for points of failure. Often times, leaks will be found in the junctions between components or at the crimped connections between flexible and ridged sections. It is a very good idea to use new gaskets and seals when replacing a power steering pressure hose, as well as flush old fluid.