A pump assembly (20) includes a rotor (40) and a stator (38) which are disposed within a housing (24) and partially define pumping chambers (56). Fluid is conducted through an inlet passage (104) to an inlet cavity (58) which is connected with the pumping chambers (56). Fluid is conducted from the pumping chambers (56) to an outlet (62) from the pump assembly (20). A tubular passage liner (112) is disposed in the inlet passage (104) and has a straight passage (138) through which fluid flow is conducted to the inlet cavity (58). The tubular passage liner (112) prevents erosion of the housing (24) during conduction through the inlet passage (104) of inlet fluid and fluid bypassed from the outlet (62) of the pump assembly (20). Projections (204 and 206) at one end of the tubular passage liner (112) are engageable with the stator (38) to limit movement of the tubular passage liner relative to the stator. The tubular passage liner (112) is installed in the inlet passage (104) by first closing a slot (180) to reduce the cross-sectional size of the tubular passage liner. The tubular passage liner (112) is then inserted into the inlet passage (104). The slot (180) is then opened to increase the size of the tubular passage liner (112).