As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING CRUISE, IT WAS OBSERVED THAT HYDRAULIC FLUID WAS NOT VISIBLE IN SIGHT GLASS OF RESERVOIR. FUEL DUMP CARRIED OUT AND AIRCRAFT RETURNED TO DEPARTURE BASE. THE HYDRAULIC LINE TO PRESSURE SWITCH WAS FOUND TO BE RUPTURED. LINE REPLACED.