What was found
DURING CRUISE, THE NR 2 ENGINE AT 240, A LOUD BANG OCCURRED WITH AN IMMEDIATE DROP IN THE EPR FROM 1.85 TO 1.60. N1 AND N2 DROPPED APPROXIMATELY 20 PERCENT FROM THE PREVIOUS SETTING. NO OTHER WARNING INDICATED. EMERGENCY DECLARED. AIR DIVERTED INTO STL. FOUND PS4 LINE AT THE TOP OF THE ENGINE BROKEN AT THE FITTING. REPLACED THE PS4 LINE PER REA D971-42069. GROUND RAN ENGINE TO TAKEOFF POWER AND CHECKED ANTI-SURGE BLEED SCHEDULING IAW DC-9 AMM 71-00-00-5. ALL SYSTEMS OPS CHECKED GOOD.