As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING A SCHEDULED INSPECTION, THE CYLINDER LEAK CHECK SHOWED 0/80 ON CYLINDER NR 3. INVESTIGATION FOUND THAT THE EXHAUST VALVE WAS BEING HELD OPEN. FURTHER INVESTIGATION SHOWED THAT THE EXHAUST VALVE SEAT WAS EXCESSIVELY WORN. THE CYLINDER WAS REPLACED WITH AN O/H CYLINDER, PN 399343 TO RECTIFY THE DEFECT. THE CYLINDER REMOVED HAD A TSO OF 99.9 HRS.