What The 4089908 Pump Is
This is a complete water pump assembly for Cummins ISX, ISX15 and QSX15 engines in the CM570-era pre-EGR, low-fan-mount configuration. Grey cast iron housing and impeller, six-vane standard-rotation impeller, and a 10-groove ribbed pulley pressed on the shaft. It bolts to the front cover and drives off the serpentine belt on that early accessory layout.
Rib count is the first thing to check. The 10-groove pulley matches the pre-EGR belt drive. Later EGR ISX builds moved the fan mount and changed the pulley, so a pump that looks similar from three feet away will not track the belt correctly. Count the grooves on the old pulley before you order anything.
The pump ships as an assembly with the pulley already installed, so there is no pressing work in the shop. Grey iron is used for the housing and impeller because it handles the thermal cycling and coolant erosion of Class-8 duty better than thin stamped or plastic impellers used on lighter applications.
Why These Numbers Cross
Cummins revised this pump several times over the ISX production run without changing what it has to do mechanically. 4025097, 4024845 and 3800495 are earlier and superseded Cummins references for the same low-mount, 10-groove pump family. 5473366 is a later Cummins number covering the same physical envelope. The mounting bolt pattern, shaft height and impeller rotation stayed constant across the supersessions.
US Motor Works US6151 is an aftermarket catalogue number built to the same envelope. It appears in cross-reference tables alongside 4089908 because it interchanges on the same engine configuration. It is listed here for identification only — PartStop is not affiliated with, endorsed by or authorized by Cummins or US Motor Works.
That said, a cross-reference is a starting point, not a fitment promise. ISX front-end configurations vary by engine serial number and by how the truck was built. Confirm against the number stamped or cast on the pump you are pulling off, or verify by engine serial number, before you commit to a part.
How These Pumps Fail
The usual first sign is coolant staining or crust below the weep hole. That is the shaft seal letting go. It often starts as a dried residue trail you only see on a cold inspection, then turns into an active drip once the system is up to pressure and temperature. Once the weep hole is wet, the pump is finished.
Bearing failure is the other common path. Grab the pulley with the belt off and check for radial play or roughness as you spin it. Any wobble, growl or belt-edge chirp that follows engine speed points at the pump bearing. A failing bearing will chew belt edges and can eventually let the pulley walk out of plane.
4089908 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 4089908. 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 | 4025097, 4024845, 3800495, 5473366 |
| US Motor Works | US6151 |
Frequently asked questions
How do I know if I need the 10-groove pump or a different one?
Count the ribs on the pulley of the pump you are removing. This assembly uses a 10-groove pulley for the pre-EGR ISX serpentine drive. If your old pulley has a different groove count, or the fan mount sits high, you are on a different configuration and this pump is not the one. Verify by engine serial number.
Does 4025097 or 5473366 cross to 4089908?
Both are listed as cross-reference numbers for this pump, along with 4024845, 3800495 and US6151. They cover the same low-mount, 10-groove ISX pump envelope across supersessions. Use the list to identify the part, then confirm against the number on your old pump or your engine serial number before ordering.
Should I replace the thermostat and belt at the same time?
It is common practice on a pump job since the cooling system is already drained and the belt is already off. Inspect the belt for glazing and edge damage, especially if the old pump bearing was noisy. Also check the tensioner and idler for play while you have access to the front of the engine.
Not sure it fits? We check before you pay.
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
Need the part, not just the reading?
Every part below is a Premium Quality aftermarket Direct Replacement with published OEM cross-reference numbers, a 6+ month warranty and same-business-day shipping from Tacoma, WA. Not sure it fits? Run your VIN — or call and a person who knows trucks will verify fitment before you pay.