The basic principle of power steering—hydraulics—hasn't changed much since the Mustang was introduced nearly a half century ago. It has been said you could move the world with the fluid power of hydraulics. Fortunately, all we have to do is steer two front wheels with a hydraulic pump, hoses, control valve, and a power cylinder ram.
Bendix power-assisted steering isn't unique to the Mustang and other vintage Fords. It was also used on the Corvette from the mid-1960s until 1982, to name one Detroit nameplate. Farm tractors and other types of implements have also employed Bendix power steering. The downside to the Bendix system is its potential for leaks and erratic operation. Bendix power steering has a spool-type control valve and ram with multiple lines and connections, all susceptible to leakage. These unions leak mostly because they haven't been serviced properly, which can distort fittings and lines, ranging from improper hose routing to not getting a flare seated properly before tightening.
Power cylinder rams do develop leaks over time, leaving spots on your garage floor, because rams and seals wear out. These precision pieces were factory assembled and welded together under controlled conditions. They are not user serviceable. If replacing the seals and wipers doesn't stop leakage, the ram assembly must be replaced.
This is all you need to know about the Bendix steering cylinder: it cannot be completely rebuilt by the user. This seal/wiper package holds hydraulic fluid pressure inside while keeping the ram lubricated and clean. Seal replacement is something you can do on the car, though it is suggested you remove and service on a workbench. The power cylinder assembly is welded together at each end with a ram and piston installed inside. The piston is fitted with either a Teflon or iron ring designed to contain pressure. Normal system pressure is around 1,100 to 1,500 psi, which is why the ends are welded.