What This Cooler Does
The oil cooler sits in the coolant passage on the left side of the block, under the oil filter head. Hot engine oil runs through the stacked plate core while coolant passes around it. Fourteen plates give the core its surface area. Lose that heat transfer and oil temperature climbs, viscosity drops, and bearing and turbo life goes with it.
This is an aftermarket direct replacement built in aluminum, with a 14-plate core matched to the Cummins ISX, ISX15 and QSX15 application. It is intended for Class-8 over-the-road duty, which is where these coolers see the most thermal cycling and the most failures.
Coolers are commonly supplied with gaskets, but confirm what is in the box before you tear the engine down. If gaskets are not included, have the seal kit on the bench before the filter head comes off.
Why These Numbers Cross
4955831 supersedes and shares the same 14-plate core envelope as 4965487, 4955830 and 4965482. These are running changes on the same Cummins ISX family cooler — port locations, plate count, mounting bolt pattern and sealing surfaces stay the same, so a housing built for one accepts the others.
That is why a truck built with 4955830 or 4965482 on the block will show 4955831 or 4965487 on a later parts lookup. The number stamped or tagged on the old unit is the most reliable starting point, not the number on the invoice from the last owner.
Cross-reference identifies the part. It does not confirm fitment. Verify by engine serial number, or by matching the number on the cooler you pulled, before you order. Cummins made mid-production changes on ISX blocks and a number match on paper is not a guarantee on the bench.
Diagnosing A Failed Cooler
The classic failure is an internal crack or a plate seam letting go. Under pressure, oil crosses into the coolant. Pull the surge tank cap and look for a film or brown sludge on the coolant surface. If the engine sits overnight, coolant can migrate the other way and show up as milky residue on the dipstick or a high oil level.
External leaks show as coolant weeping from the cooler-to-block joint or the filter head gasket. That is often just a gasket, so clean the area and re-check before condemning the core. Pressure test the cooler off the engine if you want proof.
Before reassembly, flush the cooling system. Oil contamination attacks seals and water pump components and will come back at you on the next job.
4955831 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 4955831. 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 | 4965487, 4955830, 4965482 |
Frequently asked questions
Does 4955831 replace 4955830?
They are part of the same Cummins ISX 14-plate oil cooler family and share the same core layout and mounting. 4955831 is commonly used where 4955830 was originally installed. Confirm against your engine serial number or the number on the old cooler before ordering.
How many plates does my ISX cooler have?
Count them on the removed unit. ISX and ISX15 blocks were built with more than one core height, and this listing covers the 14-plate version only. If your old cooler has a different plate count, this is not the right part for that block.
Do I need to flush the cooling system after replacing the cooler?
Yes, if oil crossed into the coolant. Oil degrades hoses, seals and water pump components and will keep circulating after the new cooler goes on. Flush the system, change the coolant filter if fitted, and run a fresh charge of coolant.
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.