The Cummins bypass kit was built out of necessity for the higher horsepower applications. The factory cooling system was originally designed for that 300-350 horsepower range but when power is increased, there is also an increased demand on the cooling system.
Your factory thermostat is located on the front of the engine which leads to the rear cylinders to suffer from lack of coolant flow, which in turn experience the highest coolant temperatures. And it doesn’t help that cylinder 5 and 6 typically run hotter due to restrictions in the factory exhaust manifold.
This can cause excessive pressure in your cooling system and has the potential of blowing a freeze plug under high stress or high boost scenarios, which usually is the most inconvenient time for your truck to fail on you.
What Fleece Performance did was designed this coolant bypass kit with a secondary thermostat, unlike other brands, this kit works off coolant temperature vs running off excess pressure. This solves the problem before pressure becomes the issue. Fleece uses a 180 degree thermostat in their kit which mirrors the factory thermostat, doing this you now get equal temperature coolant feeding through the block.
The Fleece Performance Coolant bypass kit is not only functional but it is high quality, good looking product. All billet Aluminum, Black anodized, uses high quality AN o-ring fittings, and AN hose connections with braided hose to ensure a leak free install. Also comes with longer bolts for the thermostat spacer, and a brillo pad to clean any debris around the rear freeze plug before installing the thermostat housing.
And now all 03+ kits include the billet hose brackets.