The Ford 4C3Z-9C166-AA Combined Fuel and Oil Filter Housing is a genuine Motorcraft/Ford OEM replacement assembly engineered specifically for 2004.5–2007 Ford Super Duty trucks and Excursions equipped with the 6.0L Powerstroke diesel engine (built after February 4, 2004). Cast and machined to rigorous original equipment tolerances, this dual-chamber assembly houses both the secondary engine-mounted fuel filter and engine oil filter, restoring factory structural integrity, leak-free fluid containment, and proper oil drain-back valve function.

Quick Specs & Kit Inclusions

• Application: Engine valley mounted secondary fuel filter and oil filter dual housing assembly
• Build Date Fitment: Late-build 6.0L engines built on or after 02/04/2004 (Indianapolis plant engine serial #6240241+; Huntsville plant engine serial #117667+)
• Material Construction: Heavy-duty die-cast aluminum alloy and composite filter towers engineered to withstand severe thermal expansion and engine vibrations
• Manufacturing Standard: Genuine Ford Original Equipment Manufacturer (OEM) component
• Emissions Status: 50-state legal (direct OE replacement part)
• Direct Interchange Part Numbers: Ford 4C3Z-9C166-AA, 4C3Z9C166AA
• What's in the Box: (1) Genuine Ford Fuel and Oil Filter Dual Housing Assembly with integrated oil drain-back valve and base seals (Note: Fasteners are self-tapping; reuse existing factory mounting bolts)

Problem Solved: Curing Stripped Threads, Valley Leaks & Oil Drain-Back Failure

Years of maintenance cycles, overtightened aftermarket billet filter caps, and intense engine valley heat cycles frequently destroy the factory dual filter housing on late 6.0L Powerstrokes. Common failure modes include stripped or cross-threaded cap threads on the fuel or oil towers, hairline cracks in the aluminum body, cracked internal fuel standpipes, and stuck or broken oil drain-back valves. A malfunctioning drain-back valve allows engine oil to drain out of the filter housing into the crankcase during key-off, causing oil starvation and extended crank times on cold starts. Compromised fuel bowl threads or regulator mounting bosses result in continuous diesel fuel pooling in the engine valley. Installing the genuine Ford 4C3Z-9C166-AA restores unstripped threads, factory-sealed fluid separation, and rapid oil pressure buildup.

Fitment

• 2004.5–2007 Ford F-250 Super Duty 6.0L Powerstroke Turbo Diesel (Built After 02/04/2004)
• 2004.5–2007 Ford F-350 Super Duty 6.0L Powerstroke Turbo Diesel (Built After 02/04/2004)
• 2004.5–2007 Ford F-450 Super Duty 6.0L Powerstroke Turbo Diesel (Built After 02/04/2004)
• 2004.5–2007 Ford F-550 Super Duty 6.0L Powerstroke Turbo Diesel (Built After 02/04/2004)
• 2004.5–2005 Ford Excursion 6.0L Powerstroke Turbo Diesel (Built After 02/04/2004)
• Fitment Note: For late-build 2004 models with square-style EGR coolers; does not fit early-build 2003–early 2004 engines built prior to February 4, 2004 (round EGR cooler).

Safety & Depressurization: Park on level ground, turn off ignition, and disconnect both negative battery cables. Slowly loosen both the oil filter cap (36mm or 1-7/16" socket) and fuel filter cap (24mm socket) to vent pressure and allow trapped oil and fuel to drain into their respective reservoirs. Fluid Evacuation: Remove the oil and fuel filter elements. Use a vacuum fluid extractor to suction out residual diesel fuel and oil remaining at the bottom of both housing reservoirs to avoid spilling into the engine valley. Line & Sensor Disconnections: Disconnect the engine oil temperature (EOT) and engine oil pressure (EOP) sensor electrical pigtails. Disconnect the fuel supply tube, fuel return tube, and left-head fuel feed line from the housing using appropriate line wrenches. Housing Removal: Remove the fuel pressure regulator housing from the side of the fuel bowl (T27 Torx). Unbolt the main housing mounting bolts securing the assembly to the engine oil cooler base. Carefully lift the dual housing assembly out of the engine valley. Base Inspection & Cleaning: Clean the mounting deck on top of the oil cooler cover thoroughly with lint-free cloths and brake cleaner. Inspect the sealing surfaces for scoring or residual gasket debris. Housing Installation: Ensure new base O-rings and seals are positioned correctly. Lower the new Ford 4C3Z-9C166-AA housing onto the oil cooler cover. Hand-thread the factory self-tapping mounting bolts to ensure proper thread alignment. Torque Targets: Housing-to-Oil Cooler Base Mounting Bolts: Torque evenly in an alternating sequence to 11 ft-lbs (15 Nm). Fuel Pressure Regulator Cover Screws (T27 Torx): Torque to 45–55 in-lbs (5–6 Nm). Fuel Supply & Return Line Tube Nuts: Torque to 15–18 ft-lbs (20–24 Nm). Filter Installation: Install new Motorcraft fuel and oil filter elements. Lubricate cap O-rings with clean engine oil/diesel. Torque the oil filter cap to 18 ft-lbs (24 Nm) and the fuel filter cap to 19 ft-lbs (25 Nm). Priming & Leak Verification: Reconnect battery terminals. Cycle the ignition key to "RUN" for 30 seconds without cranking; repeat 4 times to fill the secondary fuel bowl and purge air. Start the engine and inspect housing perimeters, line junctions, and the engine valley for complete leak-free operation.