A rear cylinder coolant bypass for Ram 6.7 Cummins is a cooling-system upgrade designed to improve coolant circulation around the rear cylinders of the engine. It is commonly used on Ram 2500 and 3500 trucks, particularly those used for towing, heavy-duty work, or performance applications.

Improve Rear Cylinder Cooling

The rear cylinders of the 6.7L Cummins can experience higher coolant temperatures because of reduced coolant flow in that area. A coolant bypass adds another coolant path to help distribute flow more evenly across the engine. Fleece Performance states that its system is designed to lower rear-cylinder coolant temperatures and maintain more consistent temperatures across all six cylinders.

The system uses a secondary thermostat that responds to temperature rather than relying only on excessive cooling-system pressure. This allows the bypass to help control temperature before pressure becomes a larger concern.

Benefits for Ram 6.7L Cummins

A rear cylinder coolant bypass for Ram 6.7 Cummins can be useful for:

• Heavy towing and hauling
• High-performance Cummins builds
• Increased boost applications
• Long periods of engine load
• Improving cooling-system consistency
• Helping reduce excessive coolant pressure

Fleece's kits use braided coolant hose and AN fittings for a clean installation and are available for multiple 6.7L Cummins generations.

Model-Year Fitment

Fitment is important because the bypass components vary between Cummins generations. Fleece currently lists separate kits for 2007.5-2012, 2013-2018, and 2019+ Ram 6.7L Cummins trucks.

For 2007.5-2018 Ram 2500 and 3500 models, the kit includes a bypass hose, thermostat housing, rear thermostat housing assembly, mounting hardware, and other application-specific components.