The gas turbine engine comprises a gas generator (66), comprised of a compressor section (11), and a power turbine section (65). The power turbine section (65) comprises a power turbine rotor (81) supported by a power turbine shaft (93), which is mechanically uncoupled from the gas generator (66). The power turbine shaft (93) has an axial cavity (511) therein, fluidly coupled to a bearing sump (521) fluidly coupled to the compressor section (11) and housing at least one bearing (106) supporting a shaft of the gas generator (66). An air venting path (527) extends from said axial cavity (511) and leads in a combustion gas flow path (515) downstream of the power turbine rotor (81).