What was found
APU AUTO SHUTDOWN IN FLIGHT AT FL380. PER FLIGHT CREW OIL QUANTITY WENT TO ZERO - TO ADD- TO .5 AND BACK TO FULL BITE CHECK OF APU CONTROLLER SHOWS HIGH OIL TEMP FOR SHUT DOWN. CHIP DETECTORS ARE CLEAN AND APU OIL FULL REPLACED OIL QTY TRANSMITTER REF AMM 49-94-04 OPS CHECK GOOD. REF FIM 49-11 FAULT TREE 882, UP TO BLOCK 9 - NEXT STEP IS TO RPL BYPASS VALVE OR OIL COOLER. REMOVED AND REPLACED OIL COOLER BYPASS VALVE PER AMM 49-27-10 RAN APU FOR 1 HOUR NO LEAKS NOTED, AND NO AUTO SHUTDOWN.