As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THERMO BYPASS VALVE FAILED LYC SB 518C. LOCKNUT WAS SO LOOSE ITS REPAIR IAW SB 518C WAS NOT POSSIBLE. MOST OF THE VALVES SUBMITTER REPORTS (APPROXIMATELY 85 TO 90 PERCENT) ARE FAILING THE INSPECTION AND REPAIRED ONLY 3 DUE TO THE EXTREMELY LOOSE LOCKNUTS. SUBMITTER STATED ANY VALVES WITH A LOOSE LOCKNUT SHOULD BE REPLACED.