What was found
(CAN) DURING MODIFICATION OF AIRCRAFT, NR 2 ENGINE OIL LINES WERE REMOVED. UPON REMOVAL OF LINES IT WAS OBSERVED THAT THE MAIN OIL FEED LINE (FROM OIL COOLER) WAS CHAFED TO A DEPTH OF 0.004 INCH. THE CHAFING OCCURRED IN THE AREA BELOW THE FORWARD ENGINE FIREWALL. THE FIREWALL HAS A STAINLESS STEEL 'TUNNEL' WHICH THE OIL LINES PASS THROUGH. THE FORWARD OUTBOARD EDGE OF THIS TUNNEL CHAFED INTO THE ALUMINUM OIL TUBE. THIS TUBE WAS REMOVED FROM SERVICE.