Hydraulic engine with piston moving inside a chamber, the working and reversing controls being inside the piston.Said engine comprises a piston (6) which is provided with an annular chamber (15) into which the fluid is admitted through two conduits (13 and 14). From said chamber (15), the fluid passes through the conduit (17), the groove (19) and the conduit (21) and then through the reversing valve (22a) and from there via the conduits (28,29) into the lower chamber (2a). The fluid contained into the upper chamber (2b) is removed through the conduits (30 and 31) traverses the valve (22a) and arrives through the conduit (32) into the groove (33). It is then removed through the conduit (34) and the chamber (35) surrounding the column (4) towards two exhaust channels (37 and 36).This engine finds an application in driving the slide valve of a self-cleaning filter.