The Ford Motorcraft 1C3Z-6A642-AA (1C3Z6A642AA) is a genuine OEM engine oil cooler tube bundle core 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. Mounted horizontally along the driver-side lower engine block between the front and rear cast-aluminum mounting headers, this multi-tube heat exchanger core transfers heat from high-pressure engine oil directly into circulating engine coolant. Manufactured to exact Ford OEM engineering specifications, it features heavy-duty brazed internal tube construction designed to withstand severe thermal expansion and high hydraulic oil pressures without cracking or leaking.

Engine oil and coolant cross-contamination, thick black engine oil pooling in the cooling system degas bottle, milkshake-like emulsified sludge in the radiator, oil weeping past flattened header seals, and elevated oil temperatures under heavy towing loads are what this genuine replacement core cures. Because base engine oil pressure (40–70 PSI) is significantly higher than cooling system pressure (16 PSI), a ruptured internal tube inside the oil cooler immediately forces engine oil into the coolant passages, coating the entire cooling system in sludge and causing rapid overheating. The Ford 1C3Z-6A642-AA replaces the corroded or breached internal tube bundle with a brand-new, factory-spec heat exchanger core to restore proper thermal regulation between the lubrication and cooling systems. It is an authentic Ford OEM replacement center oil cooler tube bundle; the front header (F4TZ-6881-B), rear filter header, mounting gaskets, and internal 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 tube bundle core guarantees exact fit and thermal transfer
• Heavy-duty brazed internal tube construction resists high-pressure hydraulic spikes
• Cures oil-in-coolant cross-contamination and cooling system sludging
• Precision-machined tube ends ensure leak-free O-ring sealing inside factory cast headers
• Driver-side lower engine block mounting location
• Replaces superseded Ford part numbers F4TZ-6A642-A and 1C3Z-6A642-A
• Authentic OEM bare center heat exchanger core (gaskets, headers, and O-rings sold separately)

Position a large drain pan underneath the driver side of the engine, open the radiator drain petcock, and completely drain the engine coolant; spin off and discard the oil filter and drain the crankcase engine oil. Unbolt the front and rear oil cooler cast header mounting bolts from the engine block and extract the entire cooler assembly out from under the truck. Place the assembly onto a sturdy workbench and separate the front and rear cast headers from the old tube bundle using a soft mallet or press (inspect the cast headers for internal pitting or cracks). Thoroughly clean the inner sealing bores of both cast headers with Scotch-Brite and brake cleaner to remove all residual corrosion and old rubber deposits. Coat new silicone O-rings generously with clean engine oil or clean petroleum jelly and roll them onto both ends of the new Ford 1C3Z-6A642-AA tube bundle core. Using a bench vise, hydraulic press, or long bar clamps, press the front and rear cast headers straight and square onto the new tube bundle until fully seated, ensuring the headers are clocked in proper alignment relative to the block mounting pads. Install new OEM composite gaskets on the block, position the assembled oil cooler back onto the driver-side engine block, and torque all mounting bolts in an alternating pattern to 18 ft-lbs (24 Nm). Install a new oil filter, refill the crankcase with 15W-40 diesel oil, thoroughly flush the cooling system with a heavy-duty cooling system cleaner if oil contamination was present, refill with a 50/50 diesel coolant mix, and run the engine to verify zero oil or coolant leaks.