Cummins 4B3.9 6B5.9-Compatible Cylinder Liner Sleeve – Model-Matched

Variant differences confirmed before bulk dispatch — Every Cummins 4B3.9 and 6B5.9 cylinder liner variant is mapped against engine serial ranges and flange dimensions to eliminate fitment surprises.

Technical Specifications

Application Suitability

Why the Same Part Number Ships in Multiple Variants

A cylinder liner that appears identical on paper can seat incorrectly if the flange variant does not match the specific engine build.

Sourcing teams regularly encounter situations where a single base reference such as 3904166 covers several liner revisions across engine generations. The 4B3.9 and 6B5.9 families evolved through multiple production runs, and dimensional changes in flange height or outer diameter were introduced without changing the primary catalog entry. [NEED_CITE: Cummins B-series engine liner dimensional revisions across production years] A liner pulled from the shelf based on number alone may physically enter the bore but fail to seat at the correct protrusion, causing coolant passage misalignment or head gasket loading issues. Cross-reference tables copied between suppliers often carry forward errors without flagging these variant breaks. Our verification process checks your engine serial against the production break points before confirming which cylinder liner revision ships.

Mapping Serial Ranges to Liner Revisions

Each engine family in the Cummins B-series lineage carries serial break points that determine which cylinder liner revision left the factory. The 4B3.9 and 6B5.9 blocks were updated incrementally, and a liner dimension that applied to early production may no longer suit a later build. We pull your engine serial number and cross-check it against the variant table before releasing a fitment confirmation. This cylinder liner is not treated as a universal drop-in — the serial range decides the revision.

Flange Height and Outer Diameter Verification

The most common fitment failure with B-family cylinder liner replacements involves flange step height. A difference of a fraction of a millimeter in the flange register can alter liner protrusion above the block deck, affecting head gasket compression and coolant sealing. We require physical measurement of the removed liner or a confirmed engine build record to verify the correct variant. The outer diameter is checked against the block bore specification to ensure the interference fit falls within the required range. [NEED_CITE: diesel engine cylinder liner interference fit and protrusion tolerance standards]

Decoding Superseded and Variant Numbers

Numbers like DS-3904166 and DS3904166OS appear in aftermarket catalogs as direct equivalents to the base 3904166, yet they represent distinct liner configurations. The oversize designation, for example, applies only to blocks that have been bored during a previous rebuild. Installing a standard-size cylinder liner in an oversize bore results in inadequate interference and potential liner movement under thermal cycling. We trace the superseded number path from your old tag or invoice and confirm whether the current revision replaces it directly or requires a variant substitution.

Specification Interpretation for Fitment Decisions

Centrifugal cast iron alloy is selected for this cylinder liner to provide uniform grain density and consistent wear characteristics across the bore surface. The honed finish is controlled to a crosshatch pattern that promotes piston ring seating during initial run-in, reducing blow-by during the critical break-in period. Flange configuration varies by engine build, and the correct step geometry ensures the liner registers positively in the block counterbore without relying on clamp load alone. Outer diameter tolerance is held to maintain the specified interference fit, preventing liner rotation or cavitation erosion on the coolant side. Standard and oversize options address both virgin-bore and previously machined blocks.

The Hidden Cost of Skipping Variant Verification

A liner that does not match the block variant forces disassembly after initial assembly — doubling labor and consuming gasket sets, piston rings, and seal kits that cannot be reused.

When a cylinder liner passes visual inspection but fails dimensional verification at the flange or OD, the engine must be torn down again. Coolant contamination of the lubrication system may occur if the liner protrusion allows leakage at the head gasket interface, potentially damaging bearings that were just replaced. [NEED_CITE: consequences of cylinder liner protrusion error on head gasket integrity] Repeat teardowns introduce the risk of thread damage to head bolt holes and disturb the alignment of components that were correctly installed the first time. Fitment verification before bulk commitment eliminates this exposure entirely.

Why Buyers Source This Cylinder Liner Through XUNPO

Our Guangzhou warehouse holds cylinder liner stock across B-family variants for fast identification and dispatch. We produce selected liner lines in our own facility and source the remainder from ISO-certified manufacturing partners, with identical quality control applied to both. Part identification is supported from a worn part number, a machine model plate photograph, or a nameplate image when the tag is painted over. Cross-reference verification covers superseded numbers and alternate references, catching catalog errors that copied tables propagate. Sample units ship for physical fitment confirmation before you commit to a full overhaul set. Our technical team confirms the correct flange variant and oversize grade against your engine serial and rebuild history.

Documentation & Verification

• Commercial invoice listing each cylinder liner variant with corresponding engine serial range
• Cross-reference sheet mapping 3904166, DS-3904166, and DS3904166OS (reference only)
• Dimensional inspection record covering flange height and outer diameter
• Warranty terms covering fitment against confirmed serial range
• Packing photographs showing liner protection and labeling before dispatch
• HS code and customs documentation support for international shipment

Fitment Check Before Installation

• Measure flange step height on the removed liner before discarding it
• Verify block counterbore depth matches the incoming cylinder liner specification
• Confirm outer diameter interference fit with a bore gauge at three clock positions
• Check coolant passage alignment by dry-fitting the liner before final pressing
• Compare liner protrusion against head gasket crush requirements
• Trial-fit one unit before pressing the full set into the block

Request a Fitment Confirmation

Send your engine model, serial number, or a photograph of the nameplate and removed liner. We return a verified fitment statement with the correct cylinder liner variant, cross-reference path, and dimensional confirmation before you place a bulk order.

Frequently Asked Questions

Q: How do I confirm this liner fits my specific Cummins engine variant? A: Provide the full engine serial number from the data plate. We cross-check it against production break points for the 4B3.9, 6B5.9, ISB, ISBE, QSB, or G-series to identify the correct flange height and outer diameter revision. A fitment confirmation is returned before any cylinder liner ships.

Q: What is the difference between 3904166 and DS3904166OS? A: The OS suffix indicates an oversize cylinder liner intended for blocks that have been bored during a previous rebuild. Installing a standard-diameter liner in an oversize bore will result in insufficient interference fit. We verify your block condition before confirming which variant applies to your engine.

Q: My old part number is superseded — is this liner the correct replacement? A: We trace the superseded number path to determine whether the current revision replaces it directly or requires a variant substitution. Some supersessions involve dimensional changes in flange geometry. Provide the old number and your engine serial, and we confirm the correct cylinder liner cross-reference.

Q: I only have the engine model, no readable part number — can you identify the right liner? A: Yes. Share a photograph of the engine nameplate or the removed cylinder liner alongside the engine model designation. We use the serial range and physical dimensions to identify the correct variant, even when the original tag is worn or painted over.

Q: Can I get a sample to test fitment before ordering in bulk? A: Sample units are available for physical fitment trials before you commit to a full overhaul set. We ship one cylinder liner with complete dimensional documentation so you can verify flange seating, bore alignment, and protrusion in your block before the remainder of the order is released.