What was found
UPON GEAR RETRACTION, BOTH HYDRAULIC PUMP AMBER LIGHTS AND HYDRAULIC LEVEL AMBER LIGHT ILLUMINATED. FLIGHT WAS ABORTED AND AIRCRAFT RETURNED TO BASE AIRPORT. ON GEAR EXTENSION BY NORMAL PROCEDURES, ALL LIGHTS EXTINGUISHED. WHEN GEAR WAS DOWN AND LOCKED, FOUND AIR RELEASE VALVE AT TOP OF MAIN RESERVOIR NOT SEATED ALLOWING FLUID TO VENT OVERBOARD. RECOMMEND IAI TO LOOK AT AFFECTED PART DESIGN FOR A MORE RELIABLE SEAL.