Cummins Coolant Bypass 94-98 12v
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. It is not necessary for use in warm climates or high horsepower applications, nor does it detrimentally affect the trucks performance when removed.
For model years 2007 – 2018 6.7L trucks, including both automatic and manual equipped transmissions, factory installed transmission fluid heat exchangers are uncommon. For customers with a 6.7L that has a heat exchanger, a heater tube can be purchased at your local Chrysler Dealership [PN:68048997AA] to complete the installation.
| Weight | 4 lbs |
|---|---|
| Dimensions | 12 × 12 × 9 in |
dethbringer01 –
Awesome kit! Highly recommended!
dethbringer01 –
Came earlier than expected, no damage will buy for all my trucks
Nate –
This is a very well made piece of equipment. Nicely designed and nicely machined, fits very well and didn’t leak, works as described, so 5 stars. Compatible with stock engine hoses / fittings, and can be upgraded with fit different plumbing if needed. Uses a 1/4″ NPT adapter for fitting to stock but maybe I’ll tap my t-stat housing to 3/8″ NPT for more flow… I would consider this an “insurance” part, you will not see immediate performance improvement, but you know that your cylinders should be getting cooled more evenly. It uses a 180 degree small block Chevy thermostat so that’s handy. I’ve noticed that my coolant temp gauge is slightly more stable, but not by much. Don’t expect any results that you can “see”… I’m going to change my main t-stat to 180 so they open at about the same time, that’s personal preference I guess. The only problem I can think of is that there’s no simple way of knowing the rear t-stat is malfunctioning… The main component of this kit is an aluminum (secondary) thermostat housing that bolts onto the rear of the engine block. You have to remove the freeze plug at the back of the block which can be challenging while the engine is in the truck. You have to use a long pry bar and a hammer to knock the freeze plug on one side ONLY to get it to flip a little so you can grab it with pliers and pull it out. DO NOT knock the freeze plug into the water jacket! I unfortunately did this (Murphy’s law) and spent the next few hours fishing the plug out of the block with a magnet. In hindsight, I should have done this during the daytime, yea… Use plenty of grease on the o-ring when installing, push it in all the way before bolting it up. My little T-stat bypass hose was old and the factory clamp was tightened to the max so it leaked coolant at first. I’d recommend having a regular little hose clamp on hand. It’s a good opportunity to flush your coolant too.