System-Matched Overhaul Gasket Kit — Each Mitsubishi S4L and S4L2 variant receives verified seal contents matched to its specific engine serial configuration, preventing mid-rebuild shortages that incomplete kits cause.
Technical Specifications
| Parameter |
Value |
| Part Number |
31A94-00081, 31A94-02060, 31A94-03020, 644.600, 31A9400081, 31A9402060, 31A9403020, 644600 |
| Product Type |
Overhaul Gasket Kit |
| Cross-Reference |
31A94-00081, 31A94-02060, 31A94-03020, 644.600 (reference only for identification purposes) |
| Engine Fitment |
Mitsubishi S4L, S4L2, S4L-T, S4L2-T, S4L2-61SD, S4L2-Y263KL, S4L2-65CAM and related variants |
| Machine Fitment |
304CR, EC25, EC35, TC35, MF2405, MM40CR, 3840, 3940, T16K, Agrokid 30, Solaris 40, LT360D |
| Head Gasket Construction |
Multi-layer steel (MLS), three stainless-steel layers with elastomer coating |
| Bore Diameter Compatibility |
92 mm |
| Cylinder Bore Seal Tolerance |
±0.02 mm |
| Rubber Component Grade |
ASTM D2000 Grade CR7 |
| Temperature Resistance |
Up to 130°C |
| Metal Sealing Bead Surface Hardness |
Exceeds 320 HV |
| Kit Contents |
Head gasket, cylinder bore seals, rubber components, torque-limiting washers |
| Condition |
New Aftermarket |
| Warranty |
3–12 months against manufacturing defects |
| Standards |
ISO 9001, ISO 4547-1, ISO 10823 |
Application Suitability
| Engine System |
Related Components |
| Cylinder head and block sealing |
MLS head gasket, bore seals, valve cover gasket, timing case seals |
| Fuel and lubrication circuit reseal |
Injector sleeve seals, oil pan gasket, oil cooler O-rings, fuel pump mounting gasket |
| Cooling system junctions |
Thermostat housing gasket, water pump seal, coolant passage O-rings |
| Valve train and timing enclosure |
Valve cover torque-limiting washers, timing case gasket, camshaft seal |
| Exhaust and emission interfaces |
Exhaust manifold gasket, turbo mounting gasket where applicable |
Why Incomplete Overhaul Gasket Kits Force Engines Back onto the Stand
A verified Overhaul Gasket Kit for Mitsubishi S4L S4L2 engine rebuild ships with every seal, gasket, and torque-limiting washer the specific engine variant requires — nothing omitted, nothing substituted.
In the Yangtze River Delta repair corridor, workshop supervisors know the frustration of opening a freshly delivered overhaul kit only to find the torque-limiting washers missing or the rubber seals made from a compound that swells on contact with diesel. The engine block is already split, the crankshaft is out, and now the rebuild stalls while someone sources a single gasket from three different suppliers. I have seen Mitsubishi S4L engines sit on benches for days because a previous rebuild used oversize pistons and the standard bore seals in the kit would not seat correctly. [NEED_CITE: engine overhaul kit completeness standards for diesel rebuild facilities]
System-Level Sealing Coverage for S4L and S4L2 Variants
This Overhaul Gasket Kit for Mitsubishi S4L S4L2 engine rebuild addresses the entire cylinder sealing system rather than just the head-to-block junction. The kit groups the MLS head gasket with cylinder bore seals, rubber components rated for sustained diesel and coolant exposure, and the torque-limiting washers that many generic kits leave out. Matching all sealing surfaces in one consignment means the rebuild technician works from a single verified parts list instead of cross-referencing multiple boxes.
Dimensional Grades and Rebuild History Verification
Engines that have already been through one overhaul may have had cylinder bores honed to an oversize dimension. Ordering a standard Overhaul Gasket Kit for Mitsubishi S4L S4L2 engine rebuild without confirming whether the previous shop installed 0.25 or 0.50 oversize pistons means the bore seals may not align with the actual bore diameter. The S4L2-65CAM and S4L2-Y263KL variants carry different suffix designations that affect gasket geometry, and an engine plate worn by years of heat and oil can make variant identification difficult. Providing the engine serial number and any known rebuild history before ordering allows the kit contents to be confirmed against the actual build configuration. [NEED_CITE: engine serial variant identification methods for Mitsubishi S4L series diesel engines]
Material and Tolerance Choices That Affect Seal Longevity
The MLS head gasket uses three stainless-steel layers with an elastomer coating that maintains sealing pressure through repeated thermal cycles — heating from combustion followed by cooling during idle periods. Cylinder bore seals are laser-cut to ±0.02 mm tolerance, aligning precisely with the 92 mm bore diameter specified for the S4L family. Rubber components carry an ASTM D2000 Grade CR7 rating, meaning they resist swelling and degradation when exposed to diesel fuel, engine oil, and ethylene-glycol coolant at sustained temperatures up to 130°C. The metal sealing beads exceed 320 HV surface hardness, preventing micro-grooving on the mating surfaces that would compromise the seal over time.

The Hidden Cost of Grade and Variant Mismatch
Fitting standard-bore seals into an engine that was previously rebuilt to oversize dimensions creates an immediate leak path between the cylinder and the water jacket. The engine may pass an initial pressure test but begin weeping coolant within the first hundred operating hours, forcing a second teardown. A head gasket made from single-layer composite material instead of MLS construction cannot handle the thermal expansion differential between the cast-iron block and aluminum head under sustained load. The cumulative cost of two full teardowns — labor, machining, replacement fluids, and lost machine availability — far outweighs the effort of verifying the kit contents before the first bolt is torqued. [NEED_CITE: diesel engine rebuild failure analysis due to incorrect gasket specification]
Why Rebuild Shops Source This Kit Here
Selected gasket lines are produced in-house while remaining components are sourced from ISO-certified manufacturing partners, all carrying the same quality control standards and warranty terms. Eight product categories — engine, hydraulic, electrical, undercarriage, cabin, seal kits, tools, and general spares — allow a complete engine overhaul job list to ship as one consignment under a single account. Orders start from one piece, so a single emergency overhaul kit can be dispatched without minimum-quantity barriers. Part identification is possible from an OEM reference number (cross-reference only), engine model designation, photograph, or nameplate image. Cross-reference verification covers superseded and alternate part numbers, and sample kits can be supplied for fitment confirmation before bulk commitment. The technical team confirms compatibility and dimensional grade against the specific engine serial variant.

Documentation & Verification
- Commercial invoice and packing list itemizing each gasket and seal by engine variant
- Part compatibility sheet listing confirmed S4L/S4L2 suffix designations with OEM cross-reference numbers (reference only)
- Dimensional quality inspection record covering bore seal diameter and MLS gasket layer thickness
- Warranty terms covering manufacturing defects for the stated warranty period
- Packing photographs showing kit contents before carton sealing
- HS code and customs documentation support for international shipment
Installation & Rebuild Sequence
- Verify bore diameter with a dial gauge before fitting cylinder bore seals to confirm standard or oversize grade
- Clean all mating surfaces to bare metal; any residual elastomer or carbon disrupts MLS head gasket seating
- Torque head bolts in the manufacturer-specified star pattern using the included torque-limiting washers
- Install rubber components with a light film of clean assembly oil to prevent lip rolling during insertion
- Pressure-test the cooling system after reassembly and inspect all gasket junctions before final panel closure
- Run the engine through a graduated load break-in cycle, re-torque head bolts after the first heat cycle if specified
Requesting a Fitment-Confirmed Kit
Submit the engine model designation, engine serial number, and any known rebuild history — including whether oversize pistons or aftermarket liners were previously installed. If the nameplate is illegible, a photograph of the block casting marks or the existing head gasket outline helps confirm the correct S4L or S4L2 variant. Our technical team will cross-check the kit contents against your specific engine build and return a verified parts list before dispatch.
Frequently Asked Questions
Q: What exactly is included in this S4L/S4L2 overhaul gasket kit?
A: The kit contains an MLS head gasket, cylinder bore seals, rubber components for fuel, oil, and coolant junctions, and torque-limiting washers for valve cover and timing case bolts. The exact contents are confirmed against your engine serial number and suffix designation to ensure no sealing surface is left uncovered during your rebuild.
Q: How do I confirm which S4L variant my engine is when the nameplate is worn?
A: Provide a clear photograph of the block casting marks, the existing head gasket shape, or any legible portion of the engine plate. Our technical team cross-references these details against the Mitsubishi S4L and S4L2 variant database to identify the correct configuration before the kit ships.
Q: Does this kit cover engines that have been previously rebuilt with oversize bores?
A: It can, but only if the oversize grade is confirmed before ordering. Provide the engine serial number and any machining records from the previous rebuild. The bore seals in the kit will then be matched to the actual cylinder bore diameter rather than the factory standard dimension.
Q: What other engine components should be inspected or replaced during this overhaul?
A: Beyond the sealing system covered by this kit, inspect piston ring end gaps, main and connecting rod bearing clearances, injector spray pattern, and water pump impeller condition. Addressing the fault that caused the original failure — such as coolant contamination or thermal overload — prevents the new gasket set from failing prematurely.