Product Description
CUMMINS 3946849 OEM 190° COOLANT THERMOSTAT – RAM 5.9L (1998.5–2002)
Keep your 1998.5–2002 Dodge Ram 2500/3500 5.9L Cummins running at the factory-engineered temperature with the genuine CUMMINS 3946849 190° coolant thermostat. This OE unit restores proper warm-up, prevents overheating, and maintains stable operating temps on VP44-equipped 24-valve trucks, making it the smart choice over generic parts-store replacements.
WHY CHOOSE GENUINE CUMMINS 3946849?
- OE 190° calibration for correct warm-up and stable operating temperature.
- Direct-fit drop-in replacement for VP44 24-valve 5.9L Cummins trucks.
- Built to Cummins material and flow specs for long service life.
- Helps protect against overheating, poor cabin heat, and extended warm-up.
- Compatible with common B-series and ISB/QSB applications when verified by ESN.
FITMENT
Automotive:
- 1998.5–2002 Dodge Ram 2500 5.9L Cummins ISB (24-Valve, VP44)
- 1998.5–2002 Dodge Ram 3500 5.9L Cummins ISB (24-Valve, VP44)
Engine Family (verify by ESN before ordering):
- Cummins 6B5.9 / B6.7
- Cummins ISB / QSB platforms where 3946849 is the specified 190° thermostat
Note: Some catalogs list 3946849 primarily for 2000–2002 trucks, but it is widely used across 1998.5–2002 ISB 24-valve applications. Always confirm by VIN or engine serial number (ESN).
WHAT'S INCLUDED
- (1) Genuine Cummins 190° Coolant Thermostat — Part No. 3946849
Seal/gaskets are not included and should be ordered separately.
RECOMMENDED CUMMINS COMPANION PARTS (CPP DIESEL)
- Thermostat Seal (O-ring): CUMMINS 3925466 OEM THERMOSTAT GASKET — rectangular ring seal for thermostat housing.
- 180° Alternative for 1998.5–2007 ISB: CUMMINS 5292742 OEM 180° THERMOSTAT – 5.9L ISB — lower-temp option for towing or hot climates.
- 180° 12-Valve Alternative (94–98): CUMMINS 3928499 OEM 180° THERMOSTAT – 5.9L 12V — ideal when servicing earlier 2nd-Gen trucks alongside your 24-valve fleet.
- 2003–2007 5.9L 190° Option: CUMMINS 5292744 OEM 190° THERMOSTAT – 5.9L (2003–2007) — correct 190° thermostat for common-rail 5.9L trucks.
INSTALL NOTES
- Drain coolant below thermostat level and clean all mating surfaces.
- Always install a new thermostat seal and inspect the housing for corrosion.
- Torque thermostat housing fasteners to the factory specification.
- Refill with the correct coolant mix, bleed air, and verify heater and fan operation.
FAQ
WILL CUMMINS 3946849 FIT MY 1998.5–2002 5.9L CUMMINS RAM?
Yes. 3946849 is the genuine 190° coolant thermostat used on most 1998.5–2002 Dodge Ram 2500/3500 5.9L ISB (24-valve, VP44) trucks. Because there are calibration and market differences, CPP Diesel still recommends verifying fitment by VIN or engine serial number (ESN) before ordering.
DOES THIS THERMOSTAT COME WITH THE SEAL OR GASKET?
No. This listing is for the thermostat only. Pair it with the Cummins rectangular ring seal 3925466 and inspect or replace your housing gasket as needed to prevent leaks.
WHAT'S THE DIFFERENCE BETWEEN THE 190° AND 180° CUMMINS THERMOSTATS?
The 190° 3946849 thermostat is the stock calibration for VP44-equipped 24-valve trucks and is ideal for everyday use, emissions strategy, and cold weather warm-up. The 180° 5292742 thermostat is often chosen by owners in hot climates or heavy tow applications who prefer slightly cooler operating temps.
IS THIS A GENUINE CUMMINS PART OR AFTERMARKET?
This is a genuine Cummins thermostat, part number 3946849, built to OE specifications for temperature calibration, flow, and durability. CPP Diesel sources directly from trusted channels so you get authentic Cummins hardware, not a generic knockoff.
SHOULD I FLUSH MY COOLANT WHEN I REPLACE THE THERMOSTAT?
At a minimum, you should top off with the correct coolant after replacing the thermostat. If the coolant is old, contaminated, or you don't know its service history, this is a perfect time to drain, flush, and refill with fresh coolant that meets the Cummins/Ram spec.
WHAT OTHER COMPONENTS SHOULD I CHECK WHILE I'M IN THE COOLING SYSTEM?
Inspect the thermostat housing, radiator cap, coolant hoses, water pump, and fan clutch or electric fan setup. CPP Diesel stocks Cummins and performance upgrades for radiators, hoses, fans, and more so you can refresh the entire cooling system while access is easy.
SPECIFICATIONS
| Brand | Cummins Genuine OEM |
|---|---|
| Part Number | 3946849 |
| Description | 190° engine coolant thermostat |
| Opening Temperature | 190°F (approx. 88°C) |
| Engine Compatibility | 5.9L Cummins ISB (1998.5–2002 VP44), select B/ISB/QSB applications (verify by ESN) |
| Chassis Compatibility | 1998.5–2002 Dodge Ram 2500/3500 5.9L Cummins |
| UPC | 193807298562 |
| GTIN | 00193807298562 |
| Cross Reference | Cummins 3935824, Cummins 3937171, Mopar 5015708AC, aftermarket kit references PAI 181907OEM (check catalog before substituting) |
| Shipping Weight | Approx. 0.25 lb (thermostat only) |
| Package Dimensions | Approx. 4 in × 4 in × 3 in (standard small-part carton) |
| Shipping Method | Standard ground; ships from CPP Diesel, shipping calculated at checkout |
| E-Codes / Emissions | Not emissions-controlling (cooling system component) |
| Prop 65 | WARNING: This product can expose you to chemicals including lead and other substances, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov. |
Bottom line: If you're chasing OEM reliability and correct operating temperature on your 1998.5–2002 Ram 5.9L Cummins, the CUMMINS 3946849 190° coolant thermostat is the right part, backed by CPP Diesel's diesel-focused inventory and support.
