Fleece Performance 98.5-02 Dodge 5.9L Cummins VP Coolant Bypass KitAnother product from Fleece Performance built out of necessity is the 1998. 5 2002 Cummins 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,