Abstract: A rotary positive displacement hydraulic machine includes a housing defining two mutually intersecting parallel working chambers having a low pressure inlet side and a high pressure outlet side. Two meshing rotors are mounted for rotation in the two chambers, respectively. Bearing supports at opposite ends of the chambers, support bearings in which the rotors are journalled for rotation. At least one end of the housing is closed by an end cover. The end cover and adjacent housing end have at least one elongate recess on each side of the working chambers. The end cover recesses are alignable with the housing recesses. There is at least one keying element in each pair of aligned recesses so that the open end of the housing is supported against relative movement by differential fluid pressure in the chambers in a direction transverse to a plane containing the axes of rotation of the meshing rotors.