What Is In The Set
This is a complete upper set, not a head gasket on its own. It covers the cylinder head gasket, camshaft (valve) cover gaskets and seals, exhaust manifold gaskets, turbocharger gasket, and thermostat housing gaskets with their O-ring seals. Everything above the deck that gets disturbed on a head pull is in the box.
Materials are mixed by application: multi-layer steel where clamp load and combustion pressure demand it, composite where the joint needs to conform, and rubber O-rings on coolant and oil passages. The MLS head gasket carries the fire ring load; the softer joints handle thermal movement on the manifold and thermostat housing.
The 15.0L inline-six ISX platform sees head gasket work for the usual reasons — coolant in a cylinder, oil in the coolant, combustion pressure pushing into the cooling system, or a cracked head found during a valve set. Once the head is off, every gasket in this set is a one-time-use item and gets replaced.
Why These Numbers Cross
4955594 is the headline number for this upper set. Cummins numbers 3800447, 3800449, 4024856, 4025045 and 4025287 cross to the same physical sealing package because they all describe an upper gasket kit for the single overhead cam, non-EGR ISX / QSX architecture with the same head bolt pattern, same fire ring diameter, and same manifold and thermostat housing flange layout.
Multiple numbers exist because kit contents were revised over the production life of the engine and because service kits were packaged differently for in-frame versus overhaul jobs. Supersession and repackaging generate new numbers without changing the sealing surfaces the gaskets have to match. That is the whole basis of the cross — the joints are identical.
These numbers are listed for identification only. PartStop is not affiliated with, endorsed by, or authorised by Cummins. A cross-reference is a starting point, not a fitment promise — confirm against the number stamped on your old kit or against your engine serial number before you order.
Check Before You Order
Single cam versus dual cam is the first thing to settle. This set fits SOHC engines only. Pull the valve cover and look — one camshaft in the head means you are in the right family. A dual overhead cam ISX takes a different upper package and the wrong kit will strand your truck with the head already off.
Second check: non-EGR. Confirm your engine configuration and then run the engine serial number off the dataplate on the block. Serial number is the reliable answer; model year and truck make are not. Freightliner Cascadia, Columbia and Coronado, Kenworth T680 and W900, Peterbilt 389 and 579, International ProStar and LT, Western Star and Volvo VNL all carried this engine in more than one build.
4955594 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 4955594. 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 | 3800447, 3800449, 4024856, 4025045, 4025287 |
Frequently asked questions
Does 4955594 include the lower gaskets for a full overhaul?
No. This is an upper set only — head gasket, cam cover, exhaust manifold, turbo and thermostat housing seals. Oil pan, rear seal, front cover and cylinder liner sealing components are not included. If you are pulling the pan or the liners, you need lower-end gaskets ordered separately.
How do I tell if my ISX is single cam or dual cam?
Take the valve cover off and count camshafts in the head. One cam is SOHC and matches this set. Two cams means a different upper gasket package. You can also confirm from the engine serial number on the block dataplate, which is the more reliable route before ordering.
Will this set work on an ISX with EGR?
This aftermarket upper set is built for single overhead cam, non-EGR ISX and QSX applications. EGR-equipped engines have additional sealing points at the EGR cooler and associated plumbing that this kit does not address. Verify your engine configuration by serial number before ordering.
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.