What was found
LEFT ENGINE INLET DEICE BOOT FAILED IN FLIGHT, OUTSIDE AIR TEMP -50. RETURNED TO PDX. INSPECTED ENTIRE DEICE SYSTEM, TIGHTEN UP NUMEROUS LINES AND REPLACED BOTH WATER SEPARATORS. INFLATED ALL BOOTS WITH SHOP AIR AND INSPECTED. OPS CHECK DEICE SYSTEM, CHECKS GOOD ON DECK (RAN 20 MINUTES). NO LEAKS DETECTED.