What was found
ON CLIMB OUT, AFTER TAKEOFF, CREW REPORTED VIBRATION FELT THROUGHOUT THE ACFT. CREW DECLARED AN EMERGENCY AND LANDED SAFELY. MX PERFORMED ENG RUNS AND ENG OPS CHECKS, CHECKED ALL FLIGHT CONTROL RIGGING, AND PERFORMED LANDING GEAR OPS AND VISUAL CHECKS BUT WAS UNABLE TO DUPLICATE THE DISCREPANCY ON THE GROUND. HOWEVER, MX VERIFICATION FLIGHT CONFIRMED THE EXISTANCE OF THE VIBRATION. MX FOUND THE COALESCER SOCK FROZEN. UPON REPLACEMENT OF THE SOCK AND SUBSEQUENT MX VERIFICATION FLIGHT, THE NOISE WENT AWAY.