What This Gasket Does
The 3104392 seals the valve cover to the cylinder head on the ISX15. It runs the full perimeter of the cover and keeps oil mist and splash inside the cam box. On a big-bore six that means a long sealing path, a lot of thermal cycling, and constant vibration from the overhead. Any hardening or crushing of the gasket shows up as a leak.
Failure is usually gradual. The material takes a compression set, loses rebound, and stops filling the groove when the engine heats and cools. You see oil creeping down the side of the head, dirt sticking to the block, and eventually drips on the frame rail or the exhaust. Burning oil smell in the cab is a common first complaint.
It is also a common casualty of any overhead job. Once the cover comes off for a valve lash and injector adjustment, the old gasket rarely seals the same way going back on. Most shops replace it as a matter of course rather than fight a leak two weeks later.
Why These Numbers Cross
The headline number 3104392 is the base reference for this gasket. FP Diesel lists the same part as FP-3104392 — the prefix is the brand's own catalog convention layered on the base number, which is why the digits stay identical. That is the clearest kind of cross: same form, same sealing profile, same application family.
Numbers cross because the part they describe is dimensionally the same. The gasket has to match the cover flange width, the groove or rail geometry, and the bolt-hole spacing on the ISX15 head. Change any one of those and you get a different part number, not a suffix. When only the prefix changes, you are looking at the same component under a different label.
These numbers are listed for identification only. PartStop is not affiliated with, endorsed by, or authorised by Cummins or FP Diesel. Use the cross-reference as a starting point, then confirm against your VIN or the number stamped or printed on the gasket you pulled off.
Before You Order
Pull the old gasket and look at it before you buy. Note whether it is one continuous piece or a multi-section cover arrangement, and check the flange face on your cover for warping. A cover that has been over-torqued or dropped will leak on a new gasket too. Straightedge the flange and replace the cover if it is bowed.
Clean the head rail completely. Old RTV, carbon, and coolant residue on the sealing surface will hold the new gasket off its seat. Torque the cover bolts to the sequence and value in your service manual — overtightening crushes the gasket and causes the same leak you just fixed. Confirm fitment by VIN or by the number on the removed part.
3104392 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 3104392. 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 |
|---|---|
| FP Diesel | FP-3104392 |
Frequently asked questions
Is FP-3104392 the same gasket as 3104392?
FP Diesel lists FP-3104392 as their catalog reference for this gasket, and the base digits match 3104392. Both point to the same valve cover sealing application on the ISX15. Confirm against the number on your old gasket or your VIN before ordering, since cover configurations can vary across a long model run.
Do I need RTV with this valve cover gasket?
Follow the engine service manual. Most ISX15 valve cover installs rely on the gasket itself for the perimeter seal, with sealant only at specific corner or step joints if the manual calls for it. Smearing RTV along the whole rail usually causes squeeze-out into the cam box and does not improve the seal.
How do I know the leak is the valve cover and not something higher up?
Clean the head and cover thoroughly, run the engine to temperature, and look for the highest wet point. Oil from a turbo drain, breather hose, or injector cup will track down over the cover and mimic a gasket leak. Dye and a UV light will settle the question in one shift.
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.
Engine parts hubs
This part runs on these engines — browse the full aftermarket parts range for each.
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.