Product Overview
Fleece Performance Coolant Bypass Kit for 1998.5–2002 Dodge/Ram 5.9L VP44 24V Cummins
The Fleece Performance Coolant Bypass Kit is designed for compatible 1998.5–2002 Dodge/Ram 2500 and Ram 3500 trucks equipped with the 5.9L VP44 24-valve Cummins diesel engine.
The rear cylinders of the Cummins engine can receive less coolant flow than the front cylinders, which may contribute to higher localized coolant temperatures and increased cooling-system pressure near the rear of the engine block.
This coolant bypass kit adds a secondary, temperature-controlled coolant circuit that helps improve coolant circulation across all six cylinders. By improving coolant flow before excessive pressure develops, the system is designed to promote more consistent engine temperatures and improved long-term cooling-system reliability.
Key Benefits
- Improved Rear-Cylinder Coolant Flow: Adds an additional coolant path at the rear of the engine.
- Balanced Cooling: Designed to help maintain more consistent coolant temperatures across all six cylinders.
- Temperature-Controlled Operation: Secondary thermostat opens according to coolant temperature rather than cooling-system pressure.
- Cooling-System Protection: Helps reduce localized pressure that can contribute to freeze-plug failures.
- Leak-Free Installation: Complete kit includes braided stainless-steel hose and AN O-ring fittings.
How the Coolant Bypass Works
The factory cooling system routes coolant from the front of the engine toward the rear, allowing the rear cylinders to experience higher coolant temperatures under heavy engine loads.
The Fleece Performance Coolant Bypass introduces a secondary coolant path equipped with its own thermostat. As coolant temperature rises, the thermostat opens and allows additional coolant to circulate from the rear of the cylinder head back into the cooling system.
Unlike pressure-operated bypass systems, the Fleece design responds directly to coolant temperature, helping improve coolant distribution before excessive pressure develops.
Cooling-System Protection
Improving coolant circulation at the rear cylinders helps reduce localized hot spots and excessive cooling-system pressure that may contribute to freeze-plug failures and other cooling-system concerns.
Actual cooling-system performance will vary depending on engine load, towing conditions, ambient temperatures, cooling-system condition, installation quality, maintenance, and other vehicle modifications.
Application Notes
This version is specifically designed for 1998.5–2002 Dodge/Ram trucks equipped with the 5.9L VP44 24-valve Cummins diesel engine.
- Engine: 5.9L VP44 24-Valve Cummins Diesel
- Model Years: 1998.5–2002
- Fuel System: VP44 Rotary Injection Pump
Coolant-Flow Comparison

Without Coolant Bypass

With Fleece Performance Coolant Bypass
Product Specifications
- Product Type: Coolant Bypass Kit
- Application: 1998.5–2002 Dodge/Ram 2500 & Ram 3500
- Engine: 5.9L VP44 24-Valve Cummins Diesel
- Bypass Operation: Temperature-Controlled Secondary Thermostat
- Hose Type: Braided Stainless-Steel Coolant Hose
- Fitting Type: AN O-Ring Fittings
- UPC: 635909310457
- Shipping Weight: 10 lbs
Certification
SEMA Certification: SC-FLC01-0124
Warranty
Installation Resources
Trademark Information
Protected under U.S. Trademark Registration Nos. 6,099,979; 6,099,980; 6,099,981; and 7,659,022.
California Proposition 65 Warning
WARNING: Cancer and Reproductive Harm — P65Warnings.ca.gov
Disclaimer
Verify fitment before ordering. Emissions, warranty, installation requirements, and local regulations may vary by vehicle and location. This coolant bypass kit is intended for compatible 1998.5–2002 Dodge/Ram 5.9L VP44 Cummins applications.
Vehicle Fitment
| Year | Make | Model | Engine |
|---|---|---|---|
| 1998.5 | Dodge/Ram | Ram 2500 / 3500 | 5.9L VP44 24-Valve Cummins |
| 1999 | Dodge/Ram | Ram 2500 / 3500 | 5.9L VP44 24-Valve Cummins |
| 2000 | Dodge/Ram | Ram 2500 / 3500 | 5.9L VP44 24-Valve Cummins |
| 2001 | Dodge/Ram | Ram 2500 / 3500 | 5.9L VP44 24-Valve Cummins |
| 2002 | Dodge/Ram | Ram 2500 / 3500 | 5.9L VP44 24-Valve Cummins |
















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