What was found
PILOT OBSERVED OIL DRIPS UNDER NR 1 ENGINE COWL. GROUNDED-YES. RUN NR 1 ENGINE AT IDLE, DID NOT OBSERVE LEAK FROM ANY DRAIN LINES, BUT LEFT SIDE OF ENGINE COWL WAS WET FROM ENGINE OIL POSSIBLE LEAK FROM HEAT EXCHANGER. FOUND HMU LEAKING ON NR 1 ENGINE. REMOVED AND REPLACED HMU, IAW ASA MTX TASK CARD N8473000 FOR REMOVAL AND TASK CARD N8473001 FOR INSTALLATION. ACCOMPLISHED TESTS 12, 3A, 13 ACTUATOR TESTS GOOD, IDLE LEAK CHECK GOOD, EEC TEST GOOD.