As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CENTER HYD SYS PRESSURE CONTINUOUSLY DROPS TO 2440 WHEN ADP ON. FOUND ADP 1 CHECK VALVE BROKEN AND BROKEN PART WEDGED IN CHECK VALVE ADP FILTER MODULE CAUSING ACMP BACKDRIVING ADP. REPLACED CHECK VALVE ADP1 AND REMOVED BROKEN PART FROM CHECK VALVE IN ADP FILTER MODULE, NOW ALL OPS OK. MAT HYD SYST TEST AND LEAK CHECK ALL OK. ALL 'C' HYD PUMP OPS CHECKED OK.