Gas turbine engine and method of providing cooling air

A buffer air pump (35) provides pressurized cooling air for cooling components of a gas turbine engine. The buffer air pump (35) is supported on and/or within an accessory gearbox (30) and draws bypass air in through an inlet manifold (32). An impeller (52) supported within a scroll housing (34) pressurizes the incoming bypass air and directs the pressurized air through passages to a component requiring cooling. The buffer air pump (35) draws in relatively cool air from the bypass flow, pressurizes the air with the impeller (52) and sends the air through conduits and passages (56) within the gas turbine engine to the component that requires cooling such as a bearing assembly.