⚠ No shipping to California due to CARB regulation.

Increased Coolant Flow, Decreased Coolant Temperatures The rear cylinders on the 5.9/6.7L Cummins suffer from a lack of coolant flow, and therefore, experience the highest coolant temperatures. This can cause excessive pressure to build in the cooling system, especially the rear of the block and blow out freeze plugs externally, or the smaller diameter plugs under the valve cover, leading to a failure. Our coolant bypass kit adds a secondary thermostat, that unlike other brands, works based on temperature instead of excessive pressure. This solves the problem before pressure becomes an issue by ensuring consistent temperatures across all six cylinders. Benefits: Lowers coolant temperature at the rear cylinders Ensures consistent temperatures across all cylinders Prevents damaging coolant pressure build up Complete kit comes with braided hose and AN O-ring fittings to ensure a leak-free installation. Kits for MY 2003+ include billet hose brackets. Why do I need a Fleece Coolant Bypass? One of the biggest issues on the 5.9/6.7L Cummins is the coolant flow problem to the rear cylinders. This can cause catastrophic failure or blow outs of the freeze plugs in an over-temperature / over-pressure condition. The Fleece Coolant Bypass is one of the most important additions you make to improve the reliability and longevity of the Cummins platform. Application Notes: The 2003 - 2007 5.9L automatic transmission version will eliminate the factory transmission fluid heat exchanger. The heat exchanger is designed for use in cold climates to warm the transmission fluid with the engine coolant.

• Billet main caps: Premium billet construction ensures stability and precision fitment. Utilizes 7/16-14 main studs and M10 side bolts along with dowels on the inner studs of the block for superior clamping and reliability.
• Enhanced design: Includes additional stock to the front and rear valley walls for increased strength along with minimum 0.625-inch skirt wall thickness.
• Priority Oil System: Oil rifling provides priority oil feed to the critical bottom-end components, reducing heat, wear, and risk of failure.
• Ductile iron sleeves: Provide a durable wear-resistant surface with improved shock absorption to handle high-performance applications.
• Complete reinforced exoskeleton combined with Hot Isostatic Pressing (HIP) ensures the highest quality casting available.
• Cross-braced lifter valley: Provides added structural integrity and individual drain backs for improved reliability.
• Heavy-duty deck thickness: Features a robust 0.750-inch deck thickness for enhanced durability.
• Lightweight: Weighs only 120 pounds with main caps, offering a strong yet lightweight solution.
• Maximized crankshaft saddle radius: Optimized for performance under high-stress conditions.
• Exclusive domed main cap design provides for maximum crankshaft support.

Vehicle Fitment