The Ford W303659 Banjo Fitting Sealing Washer is a genuine Motorcraft/Ford OEM replacement crush washer engineered specifically for the M12 fuel banjo connections on 2003–2007 Ford Super Duty trucks, Excursions, and E-Series vans equipped with the 6.0L Powerstroke diesel engine (as well as 2008–2010 6.4L applications). Designed to compress precisely under factory clamp loads, this factory-original sealing washer forms an airtight, high-integrity barrier between the cylinder head fuel rail ports and the factory fuel supply lines, eliminating fuel seepage, odor, and air intrusion.

Quick Specs & Kit Inclusions

• Application: Cylinder head fuel supply line banjo bolt sealing washer
• Thread/Fitting Size: M12 (12mm inside diameter)
• Material Construction: OEM-specification annealed copper/composite elastomer-bonded crush design engineered for diesel fuel containment
• Quantity Note: Sold individually (each banjo bolt requires two [2] washers—one on each side of the banjo line eyelet; complete engine service requires four [4] washers total)
• Manufacturing Standard: Genuine Ford Original Equipment Manufacturer (OEM) component
• Emissions Status: 50-state legal (direct OE replacement part)
• Direct Interchange Part Numbers: Ford W303659, Navistar 1845566C1
• What's in the Box: (1) Genuine Ford W303659 M12 Banjo Sealing Washer

Problem Solved: Curing Fuel Seepage, Air Intrusion & Fuel Odors

Whenever the front fuel banjo bolts on the 6.0L Powerstroke are loosened or removed—whether for injector replacement, cylinder head work, fuel pressure testing, or banjo bolt upgrades—the factory washers work-harden and take a permanent compression set. Reusing old banjo washers is a leading cause of persistent diesel fuel leaks down the front engine timing cover, severe underhood fuel odors, and hard-start conditions caused by air entering the fuel supply rail overnight. The genuine Ford W303659 provides the exact factory durometer and yield strength to seal microscopic surface irregularities on both the banjo eyelet and cylinder head mating faces without requiring excessive torque that could strip the aluminum cylinder head threads.

Fitment

• 2003–2007 Ford F-250 Super Duty 6.0L Powerstroke Turbo Diesel
• 2003–2007 Ford F-350 Super Duty 6.0L Powerstroke Turbo Diesel
• 2003–2007 Ford F-450 Super Duty 6.0L Powerstroke Turbo Diesel
• 2003–2007 Ford F-550 Super Duty 6.0L Powerstroke Turbo Diesel
• 2003–2005 Ford Excursion 6.0L Powerstroke Turbo Diesel
• 2004–2010 Ford E-Series Vans (E-350 / E-450) 6.0L Powerstroke Turbo Diesel
• 2008–2010 Ford F-250 / F-350 / F-450 / F-550 Super Duty 6.4L Powerstroke Turbo Diesel

Safety & Depressurization: Park on level ground, turn off the ignition, and disconnect both negative battery cables. Slowly loosen the secondary fuel filter cap (24mm socket) in the engine valley to bleed off residual line pressure and allow fuel to drain down. Disassembly & Cleanup: Unthread the M12 banjo bolt from the front of the cylinder head. Carefully remove and discard both used sealing washers. Clean the cylinder head port sealing face, the banjo bolt threads, and both flat mating faces of the fuel line banjo ring using brake cleaner and lint-free shop cloths; verify no dirt, old copper fragments, or burs remain. Washer Orientation & Assembly: Slide one (1) new Ford W303659 washer onto the M12 banjo bolt shank flush against the bolt head shoulder. Insert the bolt through the fuel tube banjo eyelet. Slide the second (2nd) new Ford W303659 washer onto the threaded side of the bolt so the fuel tube banjo ring is squarely sandwiched between the two fresh washers. Thread Engagement: Hand-thread the banjo bolt assembly into the cylinder head port several full turns to verify smooth, square thread engagement. (Never use a ratchet or power tool to start threads into the cylinder head). Torque Target: While holding the fuel hard line steady to prevent it from twisting or binding against nearby brackets, tighten the M12 banjo bolt using a calibrated torque wrench: Factory OE Banjo Bolts: Torque to 20 ft-lbs (27 Nm). Driven Diesel / Aftermarket Banjo Bolts: Torque to 20 ft-lbs (27 Nm). Do not over-torque; excessive clamping force distorts the banjo eyelet and can strip female cylinder head threads. Priming & Leak Verification: Retighten the secondary fuel filter cap to 19 ft-lbs (25 Nm). Reconnect both battery terminals. Turn the ignition key to the "RUN" position for 30 seconds without cranking to let the electric fuel pump pressurize the fuel rails and bleed trapped air. Repeat the key cycle 3 to 4 times. Inspect the banjo fitting perimeter with a work light and mirror to verify zero diesel weeping before starting the engine.