What This Pump Is
This is a complete aftermarket water pump assembly with a cast iron housing, a 12-groove serpentine pulley, and a dual-sealed bearing. It is built for the EGR-era ISX cooling load, which runs hotter and moves more coolant than the pre-EGR setups. The impeller is a high-volume design to keep flow up through the EGR cooler circuit.
The 12-groove pulley is the identifying feature. Count the ribs on the pulley face of the pump you are pulling off. If it does not have 12, this is not your pump, regardless of what the engine tag says. Belt rib count is the fastest visual check on the bench before you open a box.
Applications listed are Cummins ISX, ISX15 and QSX15 in the CM870 EGR configuration, covering the 2002-2007 domestic ISX. Those engines show up in Freightliner Cascadia and Columbia, Kenworth T800 and W900, Peterbilt 389, International ProStar, and Volvo VNL chassis.
Why These Numbers Cross
Cummins revised the ISX water pump several times over the CM870 production run without changing the mounting interface, the drive ratio, or the 12-rib pulley. 4089158, 4920465, 3682311, 5473364 and 5484602 are supersession steps on that same casting family. A shop that ordered any one of them years ago would receive the current version today.
The changes between those numbers were internal: seal material, bearing pack, and impeller detail. The bolt pattern, gasket face, inlet and outlet geometry and pulley offset stayed fixed. That is what makes them interchangeable in the hole. It is also why an old invoice number and the number stamped on the pump in the truck often disagree.
US6344 is the US Motor Works catalog reference for the same application. Aftermarket suppliers assign their own numbering, so the US number will never match a Cummins number visually even when the part is dimensionally identical. All of these numbers are listed here for identification only.
Check Before You Order
Get your engine serial number off the dataplate on the gear housing and verify the build against it. Cross-reference is a starting point, not a fitment promise. The number cast or stamped on the pump you are removing is the strongest confirmation you have, so read it before the old unit goes in the core bin.
Diagnose the failure while you are in there. Weep hole drip means the seal is gone and the bearing is next. Play at the pulley, a growl on a cold start, or coolant streaking down the front cover all point the same direction. Inspect the belt and tensioner at the same time, because a seized pump will have cooked both.
4089910 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 4089910. Use them to identify the part — then confirm the exact fit by VIN or the number stamped on your old unit before you order. An interchange is a starting point, not a fitment guarantee.
| Brand / Line | Cross-Reference Numbers |
|---|---|
| Cummins | 4089158, 4920465, 3682311, 5473364, 5484602 |
| US Motor Works | US6344 |
Frequently asked questions
How do I tell a 12-groove ISX pump from the other one?
Count the ribs on the pulley face. This assembly uses a 12-groove serpentine pulley. If the pump on your engine has a different rib count, the belt will not track and this is the wrong assembly. Confirm against your engine serial number before ordering.
My old pump is stamped 3682311, not 4089910. Same part?
3682311 is one of the supersession numbers in this casting family and crosses to 4089910 for the CM870 EGR ISX application. The mounting face, pulley offset and drive ratio are unchanged across those revisions. Verify against your engine serial number, since a cross-reference is a starting point rather than a guarantee of fit.
What kills these pumps on an EGR ISX?
Seal failure is the usual first sign, showing as a drip at the weep hole or coolant streaking on the front cover. Bearing failure follows, and you will hear it as a growl or feel play at the pulley. Neglected coolant and a worn tensioner both shorten pump life, so check the belt system while the front is apart.
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Run your VIN and we’ll match parts to your exact truck, or call the counter — a person who knows trucks verifies fitment by OEM number before the order ships. No wrong-box returns.
More cross-reference guides
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