As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ANNUAL INSPECTION, FOUND CARBURETOR HEAT VALVE MISSING SEAL MATERIAL. ALSO, WHERE ASSY ATTACHED TO ALUMINUM PLATE, RIVETS WERE LOOSE AND WORKING. REPLACED WITH NEW SEAL AND LARGER RIVETS. SUBMITTER RECOMMENDED TO WATCH CLOSELY DURING INSPECTIONS. SUSPECT CAUSE IS HEAVY STEEL VALVE ASSEMBLY ATTACHED TO ALUMINUM PLATE WITH AN470-3 RIVETS. NOT SUFFICIENT TO PREVENT VIBRATION AND LOOSENING OF RIVETS.