Fleece Performance Coolant Bypass Kit

Another product from Fleece Performance built out of necessity is the Coolant Bypass kit. The Cummins engine cooling system was designed to adequately cool a 300-350hp engine. When the horsepower is increased there is an increased demand on the cooling system. The rear cylinders suffer from a lack of coolant flow, and therefore, experience the highest coolant temperatures. This can cause excessive pressure to build in the system, especially the rear of the block and possibly blow out freeze plugs externally, or the smaller diameter plugs under the valve cover, leading to a failure. We’ve designed our coolant bypass kit with 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. Our kit comes with high quality AN o-ring fittings and AN hose connections with braided hose to ensure a leak free installation.

The ’03-’07 5.9L automatic transmission version will eliminate the factory transmission fluid heat exchanger. The heat exchanger is not a fluid cooler; it was designed for use in cold climates to warm the transmission fluid with the engine coolant. It is not necessary for use in warm climates or high horsepower applications, nor does it detrimentally affect the trucks performance when removed.

All '07-‘13 6.7 trucks, both automatic and manual equipped transmissions, do not have a transmission fluid heat exchanger.