Hydraulic cylinder that will automatically expunge air and self level

A hydraulic cylinder comprising a cylinder tube with an enclosed bottom end and a threaded hole in said bottom end to which a pressure line carrying fluid from a pressure scource is connected, said cylinder tube having on it's interior, vertical wall, at a predetermined and optional location near the top, a relief hole with a precisely engineered approach and a precisely engineered departure passing thru said interior, vertical wall, and opening into a relief tube attached to, and extending down the vertical exterior of said vertical wall to a point below the bottom of the said cylinder tube, said cylinder tube having in it's interior a single piece piston and rod combined, of the same diameter, with the lower portion serving as the piston, and the upper portion serving as the rod, said lower portion having a groove containing a wear ring, said lower portion has an interior opening, rising from the bottom center of the piston and intersecting with a horizontal opening entering the piston slightly above the said groove containing the wear ring, said outer opening of the horizontal opening, intersecting with a vertical transfer channel on the exterior of the piston rising to a narrowed oil retaining area of the piston, a groove containing a hydraulic seal at the upper edge of said narrowed oil retaining area, said seal causing the single piece piston and rod to extend when supplied with oil from a pressure source.