What was found
FLT 811 - KMIA-TBPB, DURING LEVEL CRUISE, NR 3 ENGINE BEGAN TO SURGE AND ALL ENGINE INDICATORS FLUCTUATED. NR 3 ENGINE WAS SHUTDOWN FOR PRECAUTIONS. AIRCRAFT DIVERTED BACK TO KMIA AND LANDED WITHOUT FURTHER INCIDENT. MAINTEANCNE REMOVED AND REPLACED NR 3 ENGINE PRBC VALVE IAW B727 MM 75-31-11. OPS CHECKED GOOD IAW PWA MM 73-00. PERFORMED ENGINE RUN PER AMJ FORM B-41 AND PWA MM 71-00, OPS CHECK GOOD. AIRCRAFT RETURNED TO SERVICE. (M)