What was found
(CAN) WHILE CLIMBING, RECEIVED A LEFT BLEED DUCT WARNING AND PLANE BEGAN TO DE-PRESSURIZE. INITIATED AN EMERGENCY DECENT. DIVERTED. CORRECTIVE ACTION: FOUND BLEED AIR LEAK AT THE LEFT AC PACK HEAT EXCHANGER INLET SLEEVE BLOWING TOWARD BLEED LEAK DETECTION LOOPS MT141 AND MT142, WHICH WERE FLAGGED BY THE MDC. ADJUSTED THE SLEEVE AND VERIFIED NO LEAKS PRESENT, ALSO REMOVED AND REPLACED THE LT PACK HOT AIR SHUTOFF VALVE IN REFERENCE TO CRJ-700 AMM 21-61-08. NO LEAKS NOTED. OPERATIONAL CHECKS GOOD AT THIS TIME. (TC# 20191003012)