The Alliant Power AP0004 is a premium, OEM-quality engine oil cooler seal and gasket kit 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. Manufactured to meet or exceed strict original equipment specifications, this complete six-piece service kit contains all the required elastomeric O-rings and composite mounting gaskets needed to reseal and remount the factory horizontal oil cooler assembly. Alliant Power utilizes heavy-duty, heat-stabilized fluoropolymer and silicone O-rings engineered to resist chemical breakdown from hot diesel oil and extended-life coolant, ensuring leak-free performance under extreme operating conditions.

External oil and coolant weeping along the driver-side frame rail, oil puddling beneath the oil filter base, loss of base engine oil pressure, and catastrophic fluid cross-contamination—where high-pressure engine oil bypasses degraded internal seals and pumps directly into the cooling system degas bottle—are what this service kit eliminates. Factory internal oil cooler O-rings undergo severe heat cycling and vibration over years of service, causing the rubber to harden, flatten, and crack. Because base engine oil pressure operates at 40–70+ PSI while the cooling system runs at 16 PSI, compromised O-rings immediately force black engine oil into the coolant passages, creating a thick sludge that ruins radiators and heater cores. The Alliant Power AP0004 restores an impervious barrier between the oil and coolant circuits without requiring the purchase of an entirely new cooler assembly. It is a complete six-piece reseal kit containing two inner O-rings, two outer O-rings, one front header-to-block gasket, and one rear header-to-block gasket; the center tube bundle (1C3Z-6A642-AA) and cast aluminum headers 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
• Complete six-piece OEM-spec oil cooler reseal kit
• Engineered with premium chemical- and heat-resistant elastomeric O-rings
• Includes precision die-cut front and rear composite header-to-block mounting gaskets
• Permanently cures external oil/coolant drips and internal oil-in-coolant contamination
• Direct replacement for OEM Ford part numbers F4TZ-6A636-A, F7TZ-6A636-AAA, 1C3Z-6C610-BA, 1C3Z-6K649-BA, and Navistar 1823182C95
• Backed by Alliant Power’s 24-Month, Unlimited-Mileage Warranty

Position a large drain pan underneath the driver side of the engine, open the radiator petcock to drain all engine coolant, spin off and discard the engine oil filter, and drain the engine oil from the crankcase. Unbolt the three rear oil filter header mounting bolts and the three front header-to-block mounting bolts, then carefully extract the complete oil cooler assembly from beneath the chassis. Set the assembly onto a clean, solid workbench and use a dead-blow mallet or wooden block to separate both cast aluminum headers from the center tube bundle. Scrape away the old front and rear block gaskets, and thoroughly clean the inner receiver bores of both cast headers using a Scotch-Brite pad and brake cleaner to remove all residual rubber, oxidation, and road grime (inspect aluminum bores for severe pitting or cracks). Generously coat the new Alliant Power O-rings and the tube bundle lands with clean engine oil or petroleum jelly (never assemble dry), rolling the inner and outer O-rings into their designated lands on both ends of the tube bundle. Using a bench vise, hydraulic press, or heavy-duty bar clamps, press each cast header straight, square, and evenly onto the tube bundle until fully seated, taking care not to shear or roll an O-ring during entry. Verify that the rotational alignment of the bolt ears matches the engine block mounting pattern, wipe the engine block mounting pads completely clean and dry, position the new composite gaskets onto the block dry (do not apply RTV silicone), and mount the assembly to the engine. Torque all front and rear header-to-block bolts in an alternating sequence to 18 ft-lbs (24 Nm). Install a fresh oil filter, fill the crankcase with 15W-40 diesel oil, fill and bleed the cooling system with a 50/50 diesel coolant mix, and run the engine up to operating temperature to inspect for leaks.