The Mahle GS33545 is an OEM-grade engine oil cooler reseal 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. Engineered to meet or exceed original equipment manufacturer (OEM) standards, this complete gasket and O-ring set includes everything needed to service, reseal, and remount the factory tubular oil cooler assembly. Mahle utilizes high-grade, heat- and chemical-resistant fluoropolymer (Viton/FKM) and silicone elastomeric O-rings alongside precision die-cut composite block mounting gaskets to maintain positive sealing under severe underhood thermal cycling and continuous hydraulic pressure spikes.

External oil and coolant drips pooling along the front driver-side frame rail, loss of engine oil pressure, coolant leaks running down the oil filter housing, and internal fluid cross-contamination—such as engine oil pushing into the coolant degas bottle or radiator—are what this reseal kit eliminates. Over high mileage and years of thermal expansion, the original factory internal O-rings harden, flatten, and crack within the cast header bores, allowing pressurized engine oil (40–70+ PSI) to weep past the seals and contaminate the lower-pressure (16 PSI) cooling system. The Mahle GS33545 restores an airtight, leak-free barrier between the lubrication and cooling circuits without the expense of purchasing a complete new cooler assembly. It is a comprehensive reseal kit including two inner O-rings, two outer O-rings, the front header-to-block gasket, and the rear header-to-block gasket; replacement cast aluminum headers and the center tubular bundle core 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 direct-fit OEM-grade reseal kit for the 7.3L Powerstroke engine oil cooler
• High-temperature, chemical-resistant O-rings resist hardening, swelling, and thermal degradation
• Includes precision die-cut front and rear composite header-to-engine block mounting gaskets
• Permanently eliminates external oil/coolant drips and oil-in-coolant cross-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 Mahle’s industry-leading sealing engineering and quality control

Position a large drain catch pan underneath the driver side of the engine, open the radiator drain petcock to evacuate 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 front header-to-block mounting bolts, then remove the complete oil cooler assembly from beneath the truck. Place the assembly onto a clean, solid workbench and use a dead-blow mallet or wooden block to tap both cast aluminum headers off the central tube bundle. Scrape away the old front and rear block gaskets, and thoroughly clean the inner sealing bores of both cast headers using a Scotch-Brite pad and brake cleaner to eliminate all corrosion, scale, and baked-on rubber deposits (inspect internal aluminum bores for heavy pitting or cracks). Generously coat the new Mahle O-rings and the tube bundle lands with clean engine oil or clean petroleum jelly (never install dry), rolling the inner and outer O-rings into their designated grooves 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 pinch or slice an O-ring during insertion. Verify the rotational alignment of the bolt flanges matches the block mounting holes, clean the engine block mounting pads completely dry and oil-free, place the new Mahle composite gaskets into position dry (do not use RTV silicone), and mount the assembly to the block. Torque all front and rear header-to-block bolts in an alternating crisscross pattern to 18 ft-lbs (24 Nm). Install a new oil filter, refill the crankcase with 15W-40 diesel oil, fill and bleed the cooling system with a 50/50 diesel coolant mix, and run the engine to operating temperature to inspect for leaks.