What This Pump Is
This is a complete aftermarket water pump assembly for the Cummins ISX, ISX15 and QSX15 platform in the low-fan-mount configuration. Cast iron housing, high-flow impeller, and a 12-groove serpentine pulley pressed on. It bolts to the front cover and moves coolant through the block and head under the loads a Class-8 truck actually sees.
Applications listed by the manufacturer include Freightliner Cascadia, Kenworth T680 and W900, Peterbilt 389 and 579, International ProStar and LT, Western Star, and Volvo VNL. Those are the trucks the engine shows up in. The engine serial number, not the truck badge, is what decides which pump you need.
The two things that separate ISX15 pumps from each other are pulley groove count and fan mount height. Count the ribs on your old pulley and look at where the fan hub sits relative to the pump body. Get either one wrong and the belt tracks off or the fan will not line up.
Why These Numbers Cross
4089909 supersedes and interchanges with Cummins 4024886, 4024886NX, 4920464 and 5473363, plus PAI Industries 181882. All of these describe the same physical pump: identical mounting flange and bolt pattern, same shaft and impeller geometry, same 12-groove pulley on the low fan mount. The numbers differ because of supersessions over the production run and because a reman unit carries the NX suffix.
4024886NX is the exchange-core version of 4024886. Same casting, same fit, different sales channel. 4920464 and 5473363 are later Cummins numbers covering the same service position. 181882 is the PAI Industries listing for the same assembly. All of them are printed here for identification only.
PartStop LLC is not affiliated with, endorsed by, or authorized by Cummins, PAI, or any OEM. A number match is a starting point. Confirm fit against your engine serial number or the casting number stamped on the pump you are pulling off.
Checks Before You Order
Pull the belt and spin the pump by hand. Roughness, side-to-side play, or a wobbling pulley means the bearing is done. A steady drip from the weep hole is the seal, and that pump will not be saved by a hose clamp or stop-leak. Coolant streaking down the front of the block from the weep hole is the classic tell.
Before the new pump goes on, inspect the fan clutch, the tensioner, and the idlers. A seized fan clutch or a stiff idler loads the pump bearing and kills the replacement early. Replace the belt while the front is open, flush the system, and use the correct coolant spec for the engine rather than topping off with whatever is on the shelf.
4089909 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 4089909. 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 | 4024886, 4024886NX, 4920464, 5473363 |
| PAI Industries | 181882 |
Frequently asked questions
How do I know if I need the 12-groove or a different pulley?
Count the ribs on the pulley of the pump you are removing. This unit has a 12-groove serpentine pulley on a low fan mount. If your old pulley has a different groove count or the fan hub sits at a different height, this is not the pump for your engine. Verify against the engine serial number.
Is 4024886NX the same pump as 4089909?
It covers the same service position. 4024886NX is the reman version of 4024886, and both interchange with 4089909 for the 12-groove low-fan-mount ISX15 and QSX15 application. Numbers are listed for identification only, so still match the casting on your old pump before ordering.
What usually kills an ISX15 water pump?
Seal failure showing as a weep-hole drip, and bearing failure from belt tension or a dragging fan clutch. Contaminated or wrong-spec coolant chews the seal faster. Check the tensioner, idlers, and fan clutch when you replace the pump, or the new one goes the same way.
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
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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.