A gas turbine engine comprising: a plurality of rotating components housed within a main compressor section and a turbine section; a first tap connected to the main compressor section and configured to deliver air at a first pressure; a heat exchanger connected downstream of the first tap; a bypass air valve (106a, 106b) configured to selectively block flow of bypass air across the heat exchanger, wherein the bypass air is lower in temperature and pressure than the air from the first tap at the first pressure; a cooling compressor connected downstream of the heat exchanger and configured to pressurize the air from the first tap to a second pressure that is greater than the first pressure; a shut off valve configured to selectively stop flow of the air through the heat exchanger and the cooling compressor; a controller configured to modulate and stop flow between the heat exchanger and the plurality of rotating components under certain power conditions of the gas turbine engine, the controller being programmed to control the bypass air valve (106a, 106b), the shut off valve, and the cooling compressor such that the flow of the air is stopped between the heat exchanger and the cooling compressor only after the controller has stopped the cooling compressor; and a monitoring system in communication with the controller, wherein the monitoring system comprises: at least one of a pressure sensor downstream of the cooling compressor and a temperature sensor downstream of the cooling compressor; a first position sensor at the bypass air valve (106a, 106b) and configured to detect when the bypass air valve (106a, 106b) is open and when the bypass air valve (106a, 106b) is shut; and a second position sensor at the shut off valve and configured to detect when the shut off valve is open and when the shut off valve is shut; wherein the monitoring system is configured to detect a position error in at least one of the bypass air valve (106a, 106b) via the first position sensor and/or the temperature sensor and the shut off valve via the second position sensor, the temperature sensor, and/or the pressure sensor, and the controller is configured to take mitigating action or send an alert for mitigating action. a plurality of rotating components housed within a main compressor section and a turbine section; a first tap connected to the main compressor section and configured to deliver air at a first pressure; a heat exchanger connected downstream of the first tap; a bypass air valve (106a, 106b) configured to selectively block flow of bypass air across the heat exchanger, wherein the bypass air is lower in temperature and pressure than the air from the first tap at the first pressure; a cooling compressor connected downstream of the heat exchanger and configured to pressurize the air from the first tap to a second pressure that is greater than the first pressure; a shut off valve configured to selectively stop flow of the air through the heat exchanger and the cooling compressor; a controller configured to modulate and stop flow between the heat exchanger and the plurality of rotating components under certain power conditions of the gas turbine engine, the controller being programmed to control the bypass air valve (106a, 106b), the shut off valve, and the cooling compressor such that the flow of the air is stopped between the heat exchanger and the cooling compressor only after the controller has stopped the cooling compressor; and a monitoring system in communication with the controller, wherein the monitoring system comprises: at least one of a pressure sensor downstream of the cooling compressor and a temperature sensor downstream of the cooling compressor; a first position sensor at the bypass air valve (106a, 106b) and configured to detect when the bypass air valve (106a, 106b) is open and when the bypass air valve (106a, 106b) is shut; and a second position sensor at the shut off valve and configured to detect when the shut off valve is open and when the shut off valve is shut; wherein the monitoring system is configured to detect a position error in at least one of the bypass air valve (106a, 106b) via the first position sensor and/or the temperature sensor and the shut off valve via the second position sensor, the temperature sensor, and/or the pressure sensor, and the controller is configured to take mitigating action or send an alert for mitigating action. at least one of a pressure sensor downstream of the cooling compressor and a temperature sensor downstream of the cooling compressor; a first position sensor at the bypass air valve (106a, 106b) and configured to detect when the bypass air valve (106a, 106b) is open and when the bypass air valve (106a, 106b) is shut; and a second position sensor at the shut off valve and configured to detect when the shut off valve is open and when the shut off valve is shut; wherein the monitoring system is configured to detect a position error in at least one of the bypass air valve (106a, 106b) via the first position sensor and/or the temperature sensor and the shut off valve via the second position sensor, the temperature sensor, and/or the pressure sensor, and the controller is configured to take mitigating action or send an alert for mitigating action.