48-17-04 DOUGLAS: Applies to All DC-4 and C-54 Aircraft Equipped With Pesco Vacuum Pumps and Separators. \n\n\tTo be accomplished not later than the date established in accordance with the provisions of special Civil Air Regulation Serial Number SR-329, or any subsequent regulation affecting this compliance date. \n\n\tIn case of malfunctioning of vacuum pumps or other vacuum pump system components, fire can occur within the lines and burn through the hose connections into the engine compartment. To prevent such occurrences a hose liner must be installed between the exhaust port vacuum pump fittings and the separator line or a stainless steel flexible hose must be installed between the pump and the separator. \n\n\t(Douglas Service Bulletin DC-4 No. 85 as revised March 10, 1948, covers this same subject.)