What was found
(CAN) DURING SCHEDULED INSPECTION, FOUND EXHAUST SEAL PLATE FROM LT ENGINE OUTBOARD EXHAUST STACK TO THE HEATED ENGINE INTAKE ANTI-ICE LIP WITH ONE BOLT MISSING AND THE REMAINING BOLTS LOOSE. THE RESULTING EXHAUST LEAK HAS CAUSED SOOT TO BUILDUP ON THE ENGINE CASES. THIS HAS CAUSED AND HIDDEN SEVERE CORROSION PITTING ON THE REDUCTION GEARBOX (RGB) CASE AND SOME BOLTS AT ENGINE FLANGE 'B'. THIS COROSSION IS BEYOND ALLOWABLE LIMITS FOR A LOCAL FIELD REPAIR PER THE PWC ENGINE MM AND WILL REQUIRE REPLACEMENT OF THE RGB CASE.