The Ford Motorcraft F81Z-6881-BA (F81Z6881BA) is a genuine OEM rear oil cooler mounting header and oil filter adapter assembly engineered specifically for 1994–2003 Ford F-250, F-350, F-450, and F-550 Super Duty and OBS trucks, 2000–2003 Ford Excursions, and 1994.5–2003 Ford E-Series vans equipped with the 7.3L Powerstroke diesel engine. Bolting directly to the driver-side rear of the engine block, this heavy-duty cast aluminum housing secures the aft end of the tubular oil cooler bundle, provides the spin-on mounting pad for the full-flow engine oil filter, and houses the critical oil pressure relief/bypass valve assembly. Manufactured directly to original Ford engineering blueprints, it guarantees true gasket mating surfaces, factory thread pitch for the oil filter nipple, and precision internal bores for leak-free O-ring sealing.

Cracked or stripped oil filter mounting threads, oil weeping around the rear block interface, oil-into-coolant contamination from warped casting bores, stuck internal oil bypass valves causing oil pressure loss or unfiltered oil circulation, and severe corrosion pitting around the tube bundle receiver are what this genuine rear assembly cures. Because the rear header handles peak base engine oil pressure (40–70+ PSI) right off the pump before sending it through the filter and cooler core, inferior or pitted aftermarket castings frequently cause gasket blowout, torn sealing O-rings, and cross-contamination between the lubrication and cooling circuits. Installing the authentic Ford F81Z-6881-BA ensures factory casting integrity, correct spring tension on the pre-installed bypass valve, and a flat block-sealing surface. It is a genuine Ford OEM rear oil cooler/filter header casting with the internal bypass valve and filter threaded adapter pre-installed; the front header (F4TZ-6881-B), center tube bundle (1C3Z-6A642-AA), mounting gaskets, and silicone O-rings are sold separately.

It fits all 1994–1997 Ford OBS and 1999–2003 Ford Super Duty F-250, F-350, F-450, and F-550 trucks, 2000–2003 Ford Excursions, and 1994.5–2003 Ford E-250, E-350, and E-450 Econoline vans equipped with the 7.3L Powerstroke turbo diesel engine.

Fitment

• 1994–1997 Ford F-250 / F-350 7.3L Powerstroke Turbo Diesel (OBS)
• 1999–2003 Ford F-250 / F-350 / F-450 / F-550 Super Duty 7.3L Powerstroke Turbo Diesel
• 2000–2003 Ford Excursion 7.3L Powerstroke Turbo Diesel
• 1994.5–2003 Ford E-250 / E-350 / E-450 Econoline Van 7.3L Powerstroke Turbo Diesel
• Genuine Ford OEM replacement casting guarantees precise alignment and factory durability
• Integrated oil filter mounting pad with pre-installed internal bypass/relief valve mechanism
• Precision-machined internal bore chamfer prevents tearing or pinching O-rings during assembly
• Direct bolt-on replacement for warped, stripped, or pitted rear oil cooler/filter headers
• Engineered to withstand heavy hydraulic oil pressure and hot engine coolant cycling
• Driver-side rear engine block mounting location
• Replaces superseded Ford part numbers F4TZ-6881-A and F81Z-6881-AA
• Genuine OEM bare rear header assembly (mounting gaskets, bundle, and O-rings sold separately)

Position a large drain pan beneath the driver side of the engine, open the radiator petcock to drain the cooling system completely, spin off and discard the oil filter, and drain the engine oil from the pan. Unbolt the three mounting bolts holding the rear filter header to the engine block, unbolt the front header mounting bolts, and carefully pull the entire oil cooler assembly out from underneath the truck. Place the assembly onto a sturdy workbench and use a wooden block or soft mallet to separate the old rear header casting from the center tube bundle (inspect the tube bundle ends for gouges or heavy corrosion). Thoroughly clean the rear engine block mounting surface using a plastic scraper and brake cleaner until it is completely dry, smooth, and free of old gasket debris. Clean and inspect the rear lands of the oil cooler tube bundle, lubricate new silicone O-rings with clean engine oil or petroleum jelly, and roll them onto the bundle end. Using a bench vise, hydraulic press, or heavy-duty bar clamps, press the new Ford F81Z-6881-BA rear header straight and square onto the tube bundle until fully seated, verifying correct rotational clocking relative to the front header and block mounting holes. Position a new OEM composite rear gasket (F7TZ-6A636-AAA) onto the block dry, lift the assembled oil cooler into place, and hand-thread all mounting bolts. Torque the rear header-to-block bolts in an alternating pattern to 18 ft-lbs (24 Nm), install a fresh Motorcraft FL-1995 oil filter, fill the crankcase with 15W-40 oil, refill and bleed the cooling system with a 50/50 diesel coolant mix, and run the engine to verify zero oil or coolant leaks.