As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) WELD AT COOLING DUCT ASSEMBLY HAS NO METAL PENETRATION. SKIN JOINT SPLIT AND IT CHAFED ON THE OIL RETURN LINE WHICH PASSED BETWEEN THIS DUCT ASSEMBLY, AND THE COMPRESSOR OF THE ENGINE. THE CHAFING WAS DEEP ENOUGH TO HAVE TO REPLACE THE LINE. VISUAL INSPECTION OF ANOTHER AIRCRAFT SHOWS A SIMILAR PROBLEM WILL OCCUR. CANADAIR HAS BEEN ADVISED.