What was found
DURING CONTROL CHECK ON TAXI OUT, NR 3 HYDRAULIC PRESS LIGHT ILLUMINATED WITH SUBSEQUENT LOSS OF TOTAL SYSTEM QUANTITY. DEPRESSURIZED SYSTEM AND RETURNED TO BLOCKS. FOUND NR 3 HYDRAULIC CHECK VALVE FAILED, VALVE CRACKED AT THREADS. REMOVED REMAINING THREADED SECTION, INSPECTED MODULE THREADS, INSTALLED NEW CHECK VALVE. LEAK AND OP CHECK NORMAL PER MM 29-11-40.