BorgWarner S300 Turbo Rebuild Service

PT Turbo rebuilds and remanufactures BorgWarner S300 turbochargers in-house at our San Bernardino, CA shop. Every unit goes through a full teardown, OEM-spec or better parts replacement, CIMAT VSR balancing, and final quality inspection before it ships back — backed by a 12-month unlimited mileage warranty and nationwide mail-in service. Commonly found on Cummins / Caterpillar / Detroit Diesel.

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Common S300 Part Numbers

The following part and SKU numbers from PT Turbo’s catalog match or cross-reference to the BorgWarner S300:

Don’t see your number? Contact PT Turbo — we’ve been matching turbo part numbers since 1978.

Trouble Codes Often Seen on Cummins / Caterpillar / Detroit Diesel Equipped with the S300

These are generic diagnostic trouble codes commonly associated with turbo boost control issues on this application. They’re triggered by the vehicle’s ECU, not the turbo itself, so confirm with a scan tool before assuming the turbocharger is at fault.

• P0299 — Turbocharger/Supercharger Boost Pressure – Low (underboost)
• P0234 — Turbocharger/Supercharger Overboost Condition

Also Known As

The BorgWarner S300 goes by several names depending on the platform it came off of and how the buyer learned the part.

• BWTS S300 / BW S300
• S300SX, S300SX-E, S364, S366, S369 (frame variants)
• Cummins ISB / ISC drop-in turbo
• Caterpillar / Detroit Diesel S300 charger
• BorgWarner Schwitzer S300
• S300 journal bearing turbo

Vehicles We Commonly See With the S300

The S300 shows up across on-highway trucks, off-road equipment, and a huge number of performance diesel builds. These are the platforms that come across our bench most often.

Cummins Applications

• 5.9L and 6.7L Cummins (ISB) in Dodge/Ram 2500 and 3500, 2003 and newer (popular as a stock replacement and S300-frame upgrade)
• 8.3L Cummins ISC in medium-duty trucks and buses
• Older 12-valve and 24-valve 5.9L swaps using S300 frames for towing and sled-pull builds

Caterpillar Applications

• C7 and C9 industrial and on-highway engines
• 3126 and C-series equipment turbos in loaders, skid steers, and generator sets
• Marine and agricultural Cat platforms running S300 frame chargers

Detroit Diesel and Heavy Equipment

• Series 40 and select Series 50 Detroit applications
• Off-road and stationary diesel power units
• Bobtail, RV chassis, and vocational trucks fitted with S300 replacements

Common S300 Failure Symptoms

• Excessive in-and-out (axial) shaft play felt when wiggling the compressor wheel by hand
• Oil seeping or pouring out the compressor or turbine side, often showing as oil in the intercooler piping
• High-pitched whine or siren noise that changes with boost, signaling worn bearings or wheel rub
• Blue or gray smoke at idle and under throttle from oil getting past the seals
• Slow spool-up and loss of top-end boost
• Grinding or rattling on shutdown as the shaft coasts down
• Visible contact marks or clipped tips on the compressor wheel
• Boost that surges or “barks” under load when the wheel and housing are mismatched

Real S300 Failures We See in Our Shop

• On the S300 units we rebuild, thrust bearing wear is the number one killer. Guys running sustained high boost on tow rigs and pulling trucks hammer the thrust surfaces, and once the thrust washer wears the shaft starts walking and oil control goes out the window.
• We frequently see shaft play from extended duty cycles, especially on Cummins ISB and Cat C7 units that idle and work hard all day. The journal bearings wear oval, you get radial play, and the wheels start kissing the housings.
• Compressor wheel contact is common when an S300 gets paired with an undersized or wrong compressor housing. The wheel tips clip the cover, you lose chunks of aluminum, and the whole rotating assembly goes out of balance.
• Coked-up oil in the center section shows up on units that got shut down hot without a cooldown. The baked oil restricts the bearing feed and accelerates both thrust and journal wear.
• Cracked or warped turbine housings turn up on the high-EGT performance and heavy-tow units, usually alongside heat-distressed turbine wheels.
• We also catch a lot of “parts store rebuilds” that were never balanced or were assembled with mismatched components, and those come back to us with the same noise and play they came in with.

Preventing Future S300 Failures

Most S300 failures we see trace back to oil and heat, and both are controllable.

• Change oil and filter on schedule with the correct spec diesel oil. Clean oil is what keeps the thrust bearing alive under boost.
• Let the engine idle 2 to 3 minutes after a hard pull or tow before shutdown so the center section sheds heat and the oil doesn’t coke.
• Give it a short warm-up before you load it hard so the bearings have oil pressure and the housings are up to temp.
• Run a boost leak check on the intercooler piping and clamps. Leaks make the turbo work harder and run hotter to hold the same boost.
• Keep the air filter clean and properly seated. Dirt ingestion erodes the compressor wheel and unbalances the shaft.
• Verify your compressor and turbine housing sizing matches your wheel. Mismatched housings are what cause the wheel contact we see.
• Check oil supply and drain lines for restriction or kinks whenever you reinstall, since starved or backed-up oil kills the bearings fast.

Common S300 Upgrade Paths

Because the S300 is such a popular performance frame, a lot of customers ask about upgrades while their unit is apart. The most common requests are upgraded billet compressor wheels for better airflow and durability, extended-tip or larger turbine wheels to support higher fuel, and a 360-degree thrust bearing to handle the high-boost loads that wear out the stock thrust setup. Towing-oriented builders often want a balanced rotating assembly with reinforced bearings for reliability rather than peak power. We can advise on which combinations fit your housing and application during teardown.

Frequently Asked Questions

How to Identify Your BorgWarner Turbo

The identification tag is typically located on the compressor housing, bearing housing, or center section of the turbocharger. It usually lists the model number, assembly number, and serial number. If you’re not sure which BorgWarner model you have, send PT Turbo a photo of the tag and we’ll help identify it before you ship anything.

PT Turbo Warranty

• 12-month, unlimited mileage warranty against defects in parts and workmanship
• Final quality inspection on every rebuild: leak test, visual inspection, actuator or wastegate function check
• In-house CIMAT VSR balancing with a balance report included
• Nationwide mail-in service — you don’t need to be local

What the S300 Rebuild May Include

• Complete teardown of all major components
• Ultrasonic or parts cleaning to remove carbon, oil residue, and contamination
• Journal bearing, thrust bearing, and seal replacement
• O-rings and hardware replacement
• Shaft and wheel inspection, with compressor or turbine wheel replacement if needed
• Wastegate inspection and actuator linkage service, when equipped
• CIMAT VSR balancing
• Final inspection

Why Customers Choose PT Turbo

• Rebuilding turbochargers, including BorgWarner, since 1978
• In-house CIMAT VSR balancing on every unit, not outsourced
• Full housing sandblasting and OEM-spec or better parts replacement
• Inspect first, quote before work begins — no surprise charges
• Nationwide mail-in service from our San Bernardino, CA shop

PT Turbo Inspection Process

Every turbocharger goes through the same evaluation before any work begins:

1. Initial evaluationcompressor wheel, turbine wheel, shaft, bearing housing, VGT assembly (if equipped), actuator, and seal surfaces are checked first.
2. Complete disassemblythe turbocharger is fully torn down and every major component is inspected individually.
3. Cleaningcomponents are cleaned to remove carbon, oil residue, rust, and contamination.
4. Measurementcritical tolerances are measured against OEM specification.
5. Reassemblyrebuilt using new wear components matched to your specific model.
6. CIMAT VSR balancingthe rotating assembly is balanced in-house, with a balance report included.
7. Final inspectionleak test, visual inspection, and actuator or wastegate function check before shipment.

No work begins without your approval. You receive a quote after inspection, not before.

Pricing

Most rebuilds require inspection before final pricing. Standard rebuild pricing depends on the turbo model, parts availability, wheel condition, shaft condition, housing damage, and whether upgrades are requested. PT Turbo inspects every turbo and sends a quote before any work begins — no surprise charges.

Related BorgWarner Models

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