What was found
FLT 631, NR 1 ENGINE FIRE WARN COMES ON INTERMITTENTLY AT CRUISE FLIGHT FL 350 3 TIMES AND BOTH FIRE LOOPS CHECKED OK AND IN DESCENT FIRE LIGHT CAME ON STEADY. COMPLETED ENG FIRE CHECKLIST (CONT) LIGHT REMAINED ON, BOTH BOTTLES DISCHARGED IN A LOOP. FOUND LOOSE CONNECTORS AT PYLON "A" AND "B" LOOPS. SECURED SAME IAW 26-10-01. OPS NORMAL. REPLACED BOTH FIRE EXT BOTTLES IAW DC-8 MM 26-20-01. NO EVIDENCE OF FIRE AT NR 1 ENGINE NOTED. AIRCRAFT RETURNED TO SERVICE. ACFT GROUNDED.