Product Description
FLEECE FPE-CLNTBYPS-CUMMINS-MAN-SS CUMMINS COOLANT BYPASS KIT 03-07 MANUAL TRANSMISSION W/ STAINLESS STEEL BRAIDED LINE
The FLEECE FPE-CLNTBYPS-CUMMINS-MAN-SS Coolant Bypass Kit is engineered to solve a critical flaw on 2003–2007 5.9L Cummins engines: excessive coolant pressure at the rear cylinders. This bypass kit adds a secondary thermostat and a high-flow return path that significantly reduces coolant pressure spikes, prevents blown freeze plugs, and dramatically improves temperature balance across the engine. The included stainless steel braided line provides superior durability and protection for high-performance street, towing, and competition trucks.
By relieving excess coolant pressure at the back of the engine, this kit helps protect head gaskets, freeze plugs, and cylinder head sealing—an essential upgrade for any 5.9L Cummins running higher RPM, heavy towing loads, or aggressive tuning.
Key Features
- Includes high-strength stainless steel braided coolant line
- Reduces coolant pressure at rear cylinders to prevent freeze plug blowout
- Improves temperature balance throughout the engine
- Billet aluminum coolant manifold for durability and precision
- Designed specifically for manual transmission 5.9L Cummins trucks
- Perfect for tuned, towing, racing, or high-mileage engines
Fitment
- 2003–2007 Dodge / Ram 2500 5.9L Cummins (manual transmission)
- 2003–2007 Dodge / Ram 3500 5.9L Cummins (manual transmission)
- Engine: 5.9L common-rail Cummins
- Does not fit automatic transmission trucks (see cross-reference below)
Cross-Reference & Related Fleece Products
Enhance your cooling and reliability with these compatible Fleece components:
- Automatic transmission version:
FLEECE FPE-CLNTBYPS-CUMMINS-SS 03-07 CUMMINS COOLANT BYPASS W/ STAINLESS STEEL LINE - High-flow feed line kit:
FLEECE FPE-HFFL-1018 HIGH FLOW FEED LINE KIT 2010–2018 CUMMINS - CP3 feed fitting:
FLEECE FPE-CP3-FEED 1/2 INCH CP3 FEED FITTING - 5.9L dual pump bracket kit:
FLEECE FPE-34610-PC 5.9L DUAL PUMP BRACKET AND HARDWARE
FAQ
Why do 5.9L Cummins engines need a coolant bypass?
The rear of the Cummins cylinder head builds excessive coolant pressure, especially under load or high RPM. A bypass provides a secondary escape path, reducing stress on freeze plugs, preventing coolant leaks, and improving overall temperature consistency.
Does this kit fit automatic transmission trucks?
No. This SKU fits manual transmission trucks only. For automatic models, use the kit linked above under Cross-Reference.
Will this help prevent head gasket failure?
Yes. By relieving rear cylinder pressure and improving thermal balance, this kit helps protect the head gasket and cylinder head from pressure-related failures.
Does the kit require drilling or tapping?
No drilling or tapping is required. The kit installs using supplied fittings, the billet manifold, and the stainless braided line for a clean bolt-on installation.
Is this kit suitable for towing or high-performance use?
Absolutely. This is one of the most important reliability upgrades for tuned, towing, racing, or heavily loaded Cummins trucks.
Specifications for FLEECE FPE-CLNTBYPS-CUMMINS-MAN-SS
| Attribute | Value |
|---|---|
| Brand | Fleece Performance Engineering |
| Part Number | FPE-CLNTBYPS-CUMMINS-MAN-SS |
| UPC | 670875714946 |
| GTIN | 670875714946 |
| Engine Compatibility | 5.9L Cummins (2003–2007) |
| Vehicle Fitment | 2003–2007 Ram 2500/3500 (manual transmission only) |
| Line Material | Stainless steel braided hose |
| Manifold Material | CNC-machined billet aluminum |
| Cross Reference | FPE-CLNTBYPS-CUMMINS-SS (automatic), FPE-34610-PC (dual pump bracket), FPE-CP3-FEED (CP3 feed fitting), FPE-HFFL-1018 (feed line kit) |
| E-Codes | Not specified |
| Country of Origin | USA (per distributor listing) |
| Shipping Weight | Approx. 3 lbs |
| Package Dimensions | Approx. 12 x 8 x 4 in. |
| Shipping Method | Standard ground |
| Prop 65 Warning | Yes – Cancer and Reproductive Harm. www.P65Warnings.ca.gov |
