What was found
DURING PART 91 REPOSITIONING LEG FROM PDK TO FXE, CREW HEARD A LOUD NOISE FROM LEFT SIDE OF AIRCRAFT WHILE IN CRUISE. NOISE QUIT AFTER 10 MINUTES AND LOW HYD PRESS LIGHT ILLUMINATED. CREW DIVERTED TO PBI AS IT HAD A LONGER AVAILABLE RUNWAY THAN FXE. INSPECTION REVEALED THAT THE LEFT HYDRAULIC PUMP HAD FAILED. REPLACED LEFT HYDRAULIC PUMP WITH OVERHAULED UNIT AND RETURNED AIRCRAFT TO SERVICE. NOTE: REMOVED HYDRAULIC PUMP WAS LAST REPAIRED BY PARKER HANNIFIN ON 4/18/2008 THEN INSTALLED ON THIS AIRCRAFT ON 5/19/2008. REASON FOR LAST REPAIR GIVEN AS "LEAKING AT CASE DRAIN"