Description

This is a fully reconditioned Garrett GT18V turbocharger, OEM part number A6470900180 (alternative 727463-5004s), for the Mercedes ML 270 CDI fitted with the OM647 diesel engine. As a variable nozzle turbine (VNT) unit, it is a critical component for engine performance, throttle response, and emissions control across the engine’s rev range, with boost levels managed by an integrated electronic actuator.

At Gap Turbos, we have seen these units in our Birmingham workshop for over three decades. The most common failures are directly related to the VNT system. Carbon and soot deposits from the exhaust stream, often exacerbated by short journey driving cycles or a malfunctioning EGR system, can cause the delicate variable vanes inside the turbine housing to seize. This seizure prevents the turbo from regulating boost pressure correctly, leading to ‘limp home’ mode, poor performance, and eventual failure of the electronic actuator motor as it struggles against the resistance. Other common issues include standard bearing wear within the central housing (CHRA) due to oil contamination or starvation, and electronic failure of the actuator’s internal position sensor.

Our reconditioning process is comprehensive. We completely disassemble the customer’s original turbocharger, subjecting every component to a thorough inspection. The housing units are aqua-blasted to remove all carbon deposits. The CHRA is rebuilt with new bearings and seals before being balanced on our VSR machine to tolerances that often exceed original factory specifications. The critical VNT mechanism is cleaned, reassembled, and calibrated for correct operation. The electronic actuator is tested, and if faulty, replaced with a new or reconditioned unit which is then calibrated to the turbocharger on a flow bench. This ensures OEM-level performance and reliability.

What this turbocharger fits

• Vehicle: Mercedes-Benz ML-Class (W163)
• Model: ML 270 CDI
• Engine Code: OM647
• Power Output: 165 HP (120 kW)
• Year Range: 2002 – 2005

We offer several service options: reconditioning of your own unit, supplying a reconditioned turbo from our stock on an exchange basis, or a complete drive-in, drive-out fitting service at our workshop. We also provide associated services such as DPF cleaning to address related emission system faults.

All our reconditioned turbochargers are supplied with a comprehensive warranty. Please contact Gap Turbos with your vehicle registration for a precise quote and to confirm availability.

Specifications

Vehicle fitment

• Mercedes ML 270 CDI

Common faults & troubleshooting

• Loss of power and vehicle entering ‘limp home’ mode: This is the most common symptom, typically caused by the VNT vanes sticking, which prevents correct boost pressure regulation.
• Engine management light (EML) on: Fault codes relating to ‘boost pressure deviation’ or ‘turbocharger actuator fault’ point directly to a problem with the turbo or its electronic controller.
• A high-pitched whistle or siren noise during acceleration: This indicates worn bearings in the turbo’s core or a possible boost leak from a split hose or loose connection.
• Visible blue or grey smoke from the exhaust: This is a sign of failing oil seals inside the turbo, allowing engine oil to leak into the intake or exhaust system and be burnt.
• Hesitation or jerky acceleration: Inconsistent boost delivery, caused by partially seized vanes or a failing actuator, can make the vehicle feel unresponsive or erratic under load.

Fitting notes for this unit

• Mandatory Oil Feed Pipe Replacement: The oil feed pipe on the OM647 engine is a common point of failure due to carbonisation restricting flow. You MUST replace the oil feed pipe, banjo bolts, and washers to avoid starving the new turbo of oil.
• Pre-Installation Priming: Before connecting the oil feed pipe, use a syringe to inject 5-10ml of fresh engine oil directly into the turbo’s oil inlet. Gently spin the compressor wheel by hand for 10-15 rotations to distribute the oil across the bearings.
• First Start Procedure: After installation is complete, crank the engine for 15 seconds without letting it start (by disconnecting injector electrical plugs) to build full oil pressure to the turbocharger. Reconnect, then start the engine and allow it to idle for at least 5 minutes before driving.
• Check Engine Breather System: A blocked crankcase ventilation system increases internal engine pressure, which can impede oil drainage from the turbo and damage the new oil seals. Ensure the system is clean and functioning correctly.
• Do Not Use Sealants: Use only the supplied gaskets for the oil drain and manifold connections. Silicone sealant can break off internally and block critical oil passages, leading to catastrophic failure.
• Check for Boost Leaks: After installation, carefully check all intake pipework from the turbo to the engine for splits, cracks, or loose clamps, as leaks will cause the turbo to over-speed.

Alternative part numbers

This turbo is also referenced by:

• 727463-5004s — GT18V Turbocharger OE 727463-5004s (Mercedes ML 270 CDI, OM647, 165hp)

Frequently asked questions