The invention relates to a piston machine which comprises: a housing with a chamber with has a substantially circle sector-shaped cross-section; a pivotal piston which is designed as a pivoting element, is arranged in the housing and comprises a first working surface, wherein the housing and the piston define at least one first variable working chamber; a drive or output which is connected to the piston; and an outlet which is arranged in the working chamber for discharging a working fluid. The housing has a cooling opening in at least one housing wall, said opening leading to the chamber at least for convectively cooling a piston side opposite the first working surface by means of a coolant.