What was found
DURING A MAIN DECK CARGO FIRE PROTECTION CHECK, SMOKE CAME OUT BOTH FLIGHT DECK VENT DIFFUSERS. RAN QRH AND SMOKE CLEARED. OPERATED PACKS WITH ENGINES AS PNUEMATIC SOURCE IAW JRH. COULD NOT DUPLICATE SMOKE IN COCKPIT. OPERATED PACKS WITH APU AS PNEUMATIC SOURCE IAW AMM 49-11-00-2, AND 21-00-00-2. COULD NOT DUPLICATE SMOKE IN COCKPIT. PERFORMED CARGO ISOLATION OPS CHECK IAW AMM 21-51-00,504. COULD NOT DUPLICATE SMOKE IN COCKPIT. PERFORMED FIM 21-00-01-3, PROCEDURE 4, DUE TO PIREP SMOKE CLEARED AFTER QRH, PRIOR TO LANDING. NO DEFECTS NOTED. REMOVED AND REPLACED HYDRAULIC RESERVOIR PRESSURIZATION MODULE AND LEFT HYD HYDRAULIC HYDRAULIC RESERVOIR DEPRESSURIZATION VALVE AS A PRECAUTION DUE TO THE LT HYDRAULIC OVERFULL BEING DISPLAYED ON EICAS AND POST FLIGHT ODOR OF HYDRAULIC FLUID IN THE THE COCKPIT. AIRCRAFT OK FOR FLIGHT.