What was found
DCA/LGA - FLT 6420 - DURING CLIMB-OUT, NR 1 ENGINE OIL PRESSURE DECREASED BELOW 35 PSI, OIL TEMPERATURE CLIMBED TO ABOVE 120 DEGREES. FOLLOWED ACM PROCEDURES SHUT DOWN NR 1 ENGINE. REPLACED OIL FILTER, FOUND LOOSE B-NUT ON OIL LINE TO LOW PRESSURE SWITCH AND TRANSMITTER. SECURED LINE, REPLACED CHAFED OIL LINE FROM FUEL OIL COOLER. RAN NR 1 ENGINE AT TAKEOFF POWER. OIL TEMPERATURE AND OIL PRESSURE CHECKED NORMAL, LEAK CHECK OK IAW MM 79-32-0 AND 79-34-0. (X)