What was found
AFTER PUSH BACK FROM GATE, SMOKE FILLED CABIN AND COCKPIT IMMEDIATELY AFTER TURNING PACKS ON. RETURNED TO GATE, CLEARED CABIN AIR, INSPECTED AND CONTINUED PER MEL. AFTER TAKEOFF, CREW EXPERIENCED SMOKE IN THE CABIN AGAIN AIRCRAFT RETURN TO TUL AND MADE AN UNEVENFUL LANDING. RETORQUED B-NUT ON HYD FUSE ABOVE AFT HEAT EXCHANGER. REMOVED AND REPLACED WATER SEPARATOR AND BAGS. LEAK AND OPS CHECKED ALL PER BOEING MM.