What This Gasket Does
The 3693798 seals the joint between the turbocharger mounting flange and the exhaust manifold on Cummins ISX engines. It sits in the hottest, highest-pressure part of the exhaust path. Everything the manifold collects has to pass through this joint and into the turbine housing without escaping. Lose the seal and you lose drive pressure, which shows up as slow spool and low boost.
It is a wear item, not a lifetime part. Heat cycling, flange warp, and repeated turbo removal all take life out of it. Any time the turbo comes off an ISX for a bearing job, cartridge swap, or actuator replacement, this gasket gets replaced. Reusing a cooked gasket to save a step is how comebacks happen.
This is a premium quality aftermarket gasket built for direct replacement service in the same location. Type is turbocharger gasket, turbo-to-manifold. It installs against the factory flange without machining or modification, assuming the flange face itself is flat and the studs are in good shape.
Why These Numbers Cross
3693798 is the headline number for this gasket. FP Diesel lists FP-3685535 and PAI Industries lists 131904 for the same turbo-to-manifold sealing position on Cummins ISX. Different suppliers, different catalog systems, same flange pattern, same bolt spacing, same port opening. That is why a search for one number keeps landing you on the others.
The numbers cross because the joint they seal has not changed dimensionally. Bolt hole centers, exhaust port profile, and flange thickness are the controlling dimensions. When those match, the part is functionally interchangeable regardless of whose number is stamped on the bag. Suppliers assign their own numbers for internal cataloging, not because the hardware differs.
These numbers are listed for identification only. PartStop is not affiliated with, endorsed by, or authorised by any original equipment manufacturer. Use the cross-reference as a starting point, then confirm against the number on the old gasket or the engine serial number before you order a box of them for the shelf.
Checks Before You Order
Pull the old gasket and read it. Most carry a number, and that number is the most reliable thing you have. If the gasket came apart or burned through, get the engine serial number off the dataplate and verify against it. VIN works too. Cross-reference tells you where to look — it does not confirm fitment on your specific unit.
While the turbo is off, straightedge the manifold flange and the turbo foot. A warped or pitted face will blow out a new gasket in short order and you will be back in there. Check the mounting studs for stretch and the nuts for thread damage. Replace anything questionable while access is easy — it is cheaper than the second teardown.
3693798 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 3693798. 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-3685535 |
| PAI Industries | 131904 |
Frequently asked questions
How do I know the turbo gasket is what's leaking and not the manifold?
Look for soot fanning out from the turbo foot rather than from the head-to-manifold joint. A leaking turbo gasket usually gives you a sharp ticking or whistle that changes with load and boost. Exhaust smell in the engine bay is another sign. Clean the area, run it, and see where the fresh soot lands.
Is 131904 the same gasket as 3693798?
PAI Industries lists 131904 for the same turbo-to-manifold position on Cummins ISX, so it is a functional cross to 3693798. FP Diesel lists FP-3685535 for the same location. Those numbers are shown for identification only. Confirm against the number on your old gasket or by engine serial before ordering.
Do I need to replace the mounting hardware with the gasket?
Not always, but inspect it. Exhaust studs live in constant heat and stretch or corrode over time. If a stud is necked down, galled, or a nut fights you coming off, replace it. New hardware lets you get an even clamp load on the new gasket, which is what makes the seal hold.
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.