As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LT HYDRAULIC QUANTITY DROPPED TO ZERO 10 MINUTES AFTER TAKE-OFF. (A) SYSTEM UNLOADED, GEAR BLOW DOWN AND EMERGENCY BRAKE SYSTEMS ACTUATED. ACCOMPLISHED AIR TURN BACK TO CMH. - FOUND PLUG O-RING ON HYDRAULIC MANIFOLD LEAKING. REMOVED AND REPLACED O-RING, LEAK CHECKED GOOD. BLED HYDRAULIC SYSTEM IAW CE750 MM CHAPTER 12-10-15, SERVICED BOTH HYDRAULIC RESERVOIRS IAW CE750 MM 12-10-15.