What was found
CAPTAINS AIRSPEED IND WENT TO ZERO ON CLIMBOUT. AFTER BEING AIRBORNE FOR 15 MINUTES A/S INDICATOR CAME UP TO 300 KTS AND REMAINED THERE. DISCONNECTED ALL PITOT LINES FROM CAPT'S AIRSPEED IND, WATER TRAP, AND PITOT TUBE. BLEW OUT PITOT LINES W/NITROGEN, REPLACED CAPT'S AIRSPEED IND, PITOT DRAIN AND PITOT TUBE. PERFORMED PITOT/STATIC CHECK. OPS AND LEAKS CHECKS GOOD, NO LEAKS NOTED IAW DC-8 MM CHAPT 34. ALL TAPE REMOVED.