Cummins 5.9 Thermostat: 12V vs 24V vs 6.7L
5.9L thermostat catalog
One displacement. Two very different parts customers.
This catalog separates Dodge/Ram 5.9 diesel truck thermostats from industrial Cummins 6BT5.9 and 6BTA5.9 parts. Start in the section that describes your application; do not treat every product carrying the words “Cummins 5.9” as interchangeable.
Dodge/Ram 5.9 12-Valve Product Shelf
1994-1998 Ram 2500 and 3500
Two current store listings explicitly publish this truck range. Choose between them from the number on the removed thermostat or a verified parts record, not from the truck year alone.
1989-1993 truck?
The products above do not publish first-generation Dodge coverage. We will not extend a 1994-1998 listing backward without evidence.
5.9L 12V vs 5.9L 24V vs 6.7L Cummins Specifications
The three engines below are related Cummins inline-six pickup engines, but they are not one thermostat application. The comparison is useful because sellers, owners and search results often shorten all three names to “Cummins thermostat” or identify a part only by truck year.
| Specification | 5.9L 12V (6BT) | 5.9L 24V (ISB) | 6.7L (ISBe) |
|---|---|---|---|
| Production years | 1989-1998 | 1998-2007 | 2007-present |
| Horsepower | 160-215 @ 2,500 RPM | 215-325 @ 2,700-2,900 RPM | 350-385 @ 2,800-3,013 RPM |
| Torque | 400-440 lb-ft @ 1,600 RPM | 420-610 lb-ft @ 1,400-1,600 RPM | 610-900 lb-ft @ 1,500-1,700 RPM |
| Configuration | Inline 6 cylinder | Inline 6 cylinder | Inline 6 cylinder |
| Displacement | 5.9 liters / 359 cubic inches | 5.9 liters / 359 cubic inches | 6.7 liters / 408 cubic inches |
| Engine block | Cast iron | Cast iron | Cast iron |
| Cylinder head | Cast iron | Cast iron | Cast iron |
| Fuel system | Direct injection; Bosch VE44 / Bosch P7100 | Direct injection; common rail beginning model year 2003 | Direct injection common rail |
| Aspiration | Turbocharged; intercooler from mid-1991 model year | Turbocharged / aftercooled | Turbocharged / aftercooled |
| Valvetrain | OHV, 2 valves per cylinder | OHV, 4 valves per cylinder | OHV, 4 valves per cylinder |
Source: Cummins, Follow the Liter – The Evolution of the Cummins 5.9L to the 6.7L Pickup Engine. The horsepower and torque figures are Cummins’ published historical ranges; the exact rating depends on model year and vehicle configuration.
What This Comparison Changes When Buying a Thermostat
5.9L 12V / 6BT
This is the mechanical 1989-1998 pickup family. The store’s clearest direct truck listings, 3934373 and 3928499, publish 1994-1998 coverage. An earlier 1989-1993 truck requires a confirmed part number rather than an assumed 12V match.
5.9L 24V / ISB
The 24-valve ISB begins in 1998 and changes to common-rail injection for model year 2003. A product advertised for a mechanical 1994-1998 12-valve truck should not be transferred to an ISB only because both engines displace 5.9 liters.
6.7L / ISBe
The 6.7L is a different displacement and later engine family. Some broad product listings may mention both 5.9L and 6.7L applications, but a 6.7L thermostat should enter this catalog only when the exact part number explicitly cross-references the relevant 5.9L engine.
The specification table identifies the engine family, not the thermostat part number.
Horsepower, torque, valve count and fuel system help distinguish the generation. Final thermostat selection still depends on the old part number, vehicle year or Cummins ESN/CPL record, opening-temperature requirement and sealing arrangement.
Industrial 6BT5.9 and 6BTA5.9 Product Shelf
Equipment buyers use a different catalog route from truck owners. Generator, loader, excavator, marine and stationary-power installations should be identified from the Cummins engine dataplate. The machine make or model is useful supporting information, but it may not identify a repower or service-replacement engine.
COMPLETE SERVICE-SET ROUTE
3917324 thermostat set
The listing names 6B5.9, 6BT5.9 and 6BTA5.9 and publishes thermostat 3917324, gasket 3920336 and bushing 3923331.
EXACT 6BT / 6BTA WORDING
3946849
3864178 / 3925473
5292738 / 4930315
These listings name 6BT or 6BTA in their current product data. The original number and ESN still decide the match.
Industrial order desk
Submit the ESN and CPL from the engine dataplate with the old thermostat number. Cummins parts tools use the engine serial number or part number to reach engine-specific records and supersessions.
Later ISB and QSB 5.9 Cross-Listed Products
Some current products bridge mechanical B-series and later electronic engine names. They remain in the catalog because they can be valid when the part number and application agree, but they are not displayed as universal 12-valve thermostats.
| Product number | Relevant catalog wording | Use it when |
|---|---|---|
| 3946849 | 6B5.9, ISB/QSB 5.9L, 6BT/6BTA and Dodge/Ram references | The old number or engine-specific record agrees |
| 5292744 / 3954830 | Dodge/Ram 2003-2007 5.9L plus B-series references | You are shopping the later truck range shown in the listing |
| 4929641 / 5292707 | 6B5.9 and ISB5.9 among a broad fitment list | The application and original number both match |
| 3917324 / 3923331 kit | 6B5.9, B5.9 and QSB5.9 among listed families | You have confirmed the required kit contents and cross-reference |
Current Cummins 5.9-Relevant Thermostat Inventory
The 12 products below are intentionally mixed: dedicated truck listings, industrial service parts and multi-engine cross-references. Read the product title and fitment details before adding a part to the cart.
Three Labels That Should Stop the Purchase
“Dodge 5.9” without diesel/Cummins
Dodge also used 5.9L gasoline-engine naming. This catalog is only for Cummins diesel applications.
“Thermostat” without coolant circuit
Oil-temperature or oil-cooler thermostatic parts are not engine coolant thermostats.
“Fits 5.9” without a full part number
Displacement is a search clue, not fitment evidence. Stop and verify the number, generation and application.
Ready to place the order?
Buy directly when the product number and published application match. If they do not, use the fitment desk before checkout. You can also review Cummins Parts Information for the official engine-specific lookup route.
Related departments: Cummins 6BT/6BTA/6BTAA 5.9 Parts Hub | Cummins 4BT thermostat
