What was found
AFTER ENGINES STARTUP HAD BURNT ACIDIC SMELL COMING OUT OF ECS. OPS NORMAL RUNNING WITH APU. SMELL DECREASED BIT WAS STILL PRESENT AFTER ABOUT 5 MINUTES. RETURNED TO MAINTENANCE DUE TO OIL BYPASS ISSUE. AFTER SHUTDOWN BAGGAGE COMPARTMENT HAD STRONG BURNING SMELL AND ACCESSORY AREA HAD STRANGE CHARRED SMELL. C/W CL350 SIL LS-CL300-01 CLEANING PROCEDURE FOR OIL IN THE BLEED AIR SYSTEM & AIR CONDITIONING PACK. OPERATED BOTH ENGINES BLEED AIR ECS, ADJUSTED THE TEMPERATURE HOT TO COLD THROUGHOUT 15-20 MINS IAW CL 350 AMM 21-60-00-710-801. NO BAD OR FOUL ODOR NOTED THROUGHOUT THE AIRCRAFT.