A fluid power apparatus (10) includes a power piston (40) dividing a working chamber (18) from a first chamber (16), the power piston (40) biased toward a rest position by a spring (17) and the piston (40) displaced by means of restricting fluid flow between the working chamber (18) and first chamber (16). In order to keep contaminants from entering the first chamber (16), a collapsible filter (80) is disposed about a piston rod (13) of the power piston (40), the filter (80) having at an end cap (88) with a central opening (91) through which extends the piston rod (13) and at an opposite end member (98) a flange (95) which serves as a seat (97) for the spring (17). The end member (98) seats sealingly against the power piston (40) while the end cap (88) has a sealing mechanism (92) about the periphery of the central opening (91) to provide sealing between the end cap (88) and input rod (13). If during operation of the fluid power apparatus (10) the end cap (88) should engage an opposite wall (15) of the first chamber (16), the filter (80) collapses and permits continued full stroke displacement of the power piston (40) without damage to the filter (80). Should the filter (80) become clogged, the spring (17) seated upon the flange (95) permits the flange (95) to lift away from the power piston (40) so that fluid may bypass the filter (80) and effect continued operation of the fluid power apparatus (10).