S200AG 178482 Turbocharger for Caterpillar 3126 & C7 7.0L

S200AG

The S200AG is the BorgWarner-platform turbocharger used on the Caterpillar 3126 and C7 7.0L diesel engines in medium-duty truck applications from 2003–2004. This is a single turbo setup with a pneumatic wastegate actuator that regulates peak boost by bypassing exhaust around the turbine wheel. The 3126/C7 powered a wide range of class 6–7 trucks — Chevy C6500/C7500, GMC TopKick, Ford F-650/F-750, and various Freightliner and International models. The S200AG carries a long list of BorgWarner interchange numbers (178482, 174201, 174202, 174200, 174193–174198, 174235) because multiple compressor housing orientations were used across different truck chassis. Our S200AG is built new with all new components, ships with the wastegate actuator and mounting gaskets, and is dynamically balanced before dispatch. We verify the part number against your engine serial first. We supply repair shops, fleet operators, and distributors with single units or volume orders.

Turbo Model

S200AG (S200AG047)

OEM / Interchange Numbers

237-5270, 237-5272, 10R-1795, 237-5271, 237-5254, 237-5250, 237-5252, 237-5253

Application

2003–2004 Caterpillar Truck with 3126 / C7 7.0L Engine

Service & Support

1-Year Unlimited-Mileage Warranty
US Stock, Fast Dispatch
Bulk Orders Welcome
White-Label Support
Fully Certified

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FAQ

The S200AG fits the Caterpillar 3126 and C7 7.0L diesel engine, used in medium-duty trucks from 2003–2004. Common applications include Chevy C6500/C7500, GMC TopKick, Ford F-650/F-750, Freightliner, and International chassis trucks running the 3126 or C7.

The BorgWarner numbers (174193 through 174202, 174235, and master number 178482) all share the same core assembly and turbine housing. The only difference is the compressor housing orientation angle — the discharge port exits at different clock positions to fit different truck chassis and intake plumbing layouts. If you are not sure which number you need, match the BorgWarner stamp on your old turbo's compressor housing, or give us the CAT OEM number and engine serial and we will cross-reference it.

Yes. Our S200AG ships complete with the pneumatic wastegate actuator and mounting gaskets included. It is ready to install.

Connect a regulated air supply (max 20 psi / 138 kPa) to the wastegate canister port and watch the actuator rod. It should move smoothly as pressure increases and return when pressure drops. If the rod does not move, the diaphragm or rod is seized. A stuck-open wastegate causes low power and black smoke; a stuck-closed wastegate causes overboosting at full load. CAT does not sell the wastegate assembly separately on this platform, so a failed wastegate means replacing the turbo.

Yes — brand new, 100% new components, dynamically balanced and inspected before dispatch. Ships with gaskets. No core charge and nothing to return. Covered by a one-year unlimited-mileage warranty.

If your truck runs a CAT 3126 or C7 7.0L diesel, then yes. The key is matching the correct BorgWarner part number for your compressor housing orientation. Give us the number stamped on your old turbo or the CAT part number from your engine, and we will confirm fitment before shipping.

Yes. We hold S200AG stock in the US and supply repair shops, fleet operators, engine rebuilders, and distributors. Single units or volume orders, priced for resale.

S200AG Turbo for CAT 3126 & C7: Specs, Wastegate, and Troubleshooting

The S200AG is one of the most widely used turbochargers in medium-duty Caterpillar applications. If you are replacing a turbo on a 3126 or C7 7.0L, here is what you need to know about this unit, why it fails, and how to get the right part number the first time.

Why so many part numbers for the same turbo?

The S200AG platform covers roughly a dozen BorgWarner numbers: 178482, 174193, 174194, 174195, 174196, 174197, 174198, 174200, 174201, 174202, and 174235. They all use the same CHRA (center housing rotating assembly) and turbine housing. The difference between them is the compressor housing orientation angle — the discharge port exits at different clock positions to fit different truck chassis and intake plumbing layouts. 178482 is the master interchange number that covers the full range. When ordering, confirm the BorgWarner number stamped on your old turbo's compressor housing. If you only have a CAT part number (like 237-5270 or 10R-1795), cross-reference it in the OEM list above.

The wastegate actuator — how it works and why it matters

The S200AG uses a pneumatic wastegate controlled by boost pressure. A canister with a spring-loaded diaphragm connects to the intake manifold via a silicone hose. At low RPM, the spring holds the wastegate valve shut so all exhaust goes through the turbine — giving the turbo full spool. As boost rises and hits the target pressure, the diaphragm pushes the actuator rod to crack open the wastegate valve, bypassing some exhaust past the turbine to cap boost.

The wastegate is one of the most common failure points on the 3126/C7 turbo. Two things go wrong:

Stuck open — the turbo never builds full boost. Symptoms: low power across the RPM range, higher exhaust temperatures, black smoke under load. Often caused by a seized actuator rod or a cracked diaphragm inside the canister.
Stuck closed — the turbo overbooosts. Symptoms: boost pressure exceeding spec at full load, which can damage the engine over time. Usually caused by carbon buildup on the wastegate flapper or the actuator rod binding in the housing.

You can test the wastegate with a regulated air supply (do not exceed 20 psi / 138 kPa). Connect it to the canister port and verify that the actuator rod moves smoothly. If the rod does not move, the canister is faulty and the turbo needs replacement — CAT does not service the wastegate separately on this platform.

Common failure patterns on the 3126/C7 turbo

Beyond the wastegate, the S200AG fails for the same reasons most truck turbos do:

Failure Mode	Root Cause	What You See
Oil starvation	Clogged or kinked oil feed line, low oil level, poor oil quality	Shaft scoring, bearing wear, seized turbo
Oil drain restriction	Blocked or kinked drain tube, high crankcase pressure	Oil leaking from compressor seal, oil in intake pipe
Foreign object damage (FOD)	Debris entering compressor or turbine side	Chipped or broken wheel blades, imbalance
Excessive exhaust heat	Rich fuel condition, late injection timing, restricted exhaust	Cracked turbine housing, warped shaft

Pre-installation checklist

A new turbo will not last if the root cause of the old failure is still present. Before bolting on the S200AG:

Flush the oil feed line with clean solvent and blow it out with compressed air. Inspect for restrictions.
Check the oil drain tube for kinks, cracks, or carbon buildup. Replace the drain gasket.
Inspect the air filter housing and intake ducting for debris. Any object that gets past the filter will hit the compressor wheel.
Verify crankcase pressure is within spec — high blowby forces oil past the turbo seals even on a brand-new unit.
Prime the new turbo before startup: pour clean engine oil into the oil inlet and rotate the shaft by hand a few turns. Then crank the engine without fuel for 15–20 seconds to build oil pressure at the bearing.
After startup, idle for 3–5 minutes before loading the engine. Let the bearing seat and build a stable oil film.
Test the wastegate actuator movement after install to confirm it is responding to boost pressure.

We inspect and balance each S200AG before it ships. See our quality process for details on how we test each unit.