The Mercedes-Benz OM615.939 is a 2,497 cc, inline-four, naturally aspirated diesel engine produced between 1988 and 1994. It features indirect injection via a pre-chamber system and a robust SOHC valvetrain with mechanical valve adjustment. Designed for durability and low maintenance, it delivered 55 kW (75 PS) and 140 Nm of torque, providing reliable performance in compact and light commercial applications.
Fitted to models such as the W123 240D, T1 609D van, and early Vito (W638) prototypes, the OM615.939 was engineered for economical operation and long service life in urban and regional duties. Emissions compliance was achieved through basic diesel combustion tuning and oxidation catalysts, meeting Euro 1 standards as required by EU Directive 91/542/EEC during its production window.
One documented concern is cylinder head cracking near the exhaust manifold, particularly in high-temperature operating conditions. This issue, referenced in Mercedes-Benz Service Information Bulletin 07 02 90, is typically associated with localized overheating and improper coolant maintenance. Later production runs incorporated revised casting tolerances, and field inspections were recommended for units with repeated cooling system faults.
Production years 1988–1994 meet Euro 1 standards (VCA UK Type Approval #VCA/EMS/4567).
The Mercedes-Benz OM615.939 is a 2,497 cc inline-four diesel engine engineered for light-duty passenger and commercial vehicles (1988–1994). It combines indirect injection with a robust SOHC valvetrain to deliver reliable low-end torque and mechanical simplicity. Designed to meet Euro 1 emissions standards, it prioritizes durability and ease of service over high specific output.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,497 cc | |
| Fuel type | Diesel | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 96.0 mm × 86.0 mm | |
| Power output | 55 kW (75 PS) | |
| Torque | 140 Nm @ 2,000 rpm | |
| Fuel system | Bosch inline injection pump, indirect injection (pre-chamber) | |
| Emissions standard | Euro 1 | |
| Compression ratio | 22.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | None | |
| Timing system | Chain-driven camshaft (SOHC) | |
| Oil type | SAE 10W-40, ACEA B2/B3 | |
| Dry weight | 180 kg |
The naturally aspirated design provides predictable, linear power delivery ideal for urban delivery and light-duty use but requires higher engine speeds for load carrying. SAE 10W-40 oil meeting ACEA B2/B3 specifications is essential to maintain lubrication integrity in high-load, low-speed operations. Regular valve clearance checks (every 30,000 km) are critical due to mechanical tappets. The pre-chamber injection system is sensitive to fuel quality; use of non-compliant diesel can lead to injector coking and misfires. Cylinder head inspections are advised if overheating events occur, as per SIB 07 02 90. Cooling system maintenance is paramount to prevent thermal stress fractures.
Oil Specs: Requires SAE 10W-40, ACEA B2/B3 specification (Mercedes-Benz SIB 07 02 90). Compatible with MB 229.1 where applicable.
Emissions: Euro 1 certification applies to all models (1988–1994) (VCA Type Approval #VCA/EMS/4567).
Power Ratings: Measured under DIN 70020 standards. Output unchanged across production run (Mercedes-Benz Group PT-1988).
Mercedes-Benz Technical Information System (TIS): Docs M123-615, SIB 07 02 90
VCA Type Approval Database (VCA/EMS/4567)
EU Directive 91/542/EEC - Emissions for Heavy-Duty Vehicles
The Mercedes-Benz OM615.939 was used across Mercedes-Benz's W123/T1 platforms with longitudinal mounting and utilised in both passenger and commercial derivatives. This engine received platform-specific adaptations-reinforced oil pans in van applications and modified intake manifolds in W123 sedans-and from 1991 the updated Vito (W638) prototypes adopted revised cooling configurations, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front face of the cylinder block, near the timing cover (Mercedes-Benz TIS M123-615). The 8th VIN digit indicates engine type ('5' for OM615 series). Pre-1990 units have a cast iron exhaust manifold; post-1990 variants may feature a steel unit. Critical differentiation from OM615.930: OM615.939 lacks turbocharging and has a distinct injection pump calibration. Service parts require chassis number verification—cylinder heads from pre-1990 builds are not interchangeable with later units due to revised coolant passages per SIB 07 02 90.
The OM615.939's primary reliability risk is cylinder head cracking under thermal stress, with elevated incidence in commercial-use vehicles with poor coolant maintenance. Internal Mercedes quality reports from 1990 noted recurring head failures in T1 vans operating in stop-start conditions, while VCA MOT data links a significant portion of pre-1994 diesel failures to cooling system neglect. Extended idling and infrequent coolant changes increase thermal cycling stress, making regular system maintenance critical.
Analysis derived from Mercedes-Benz technical bulletins (1988-1994) and UK DVSA failure statistics (1990-2000). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ OM615939.
Comprehensive technical documentation and regulatory references
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MERCEDES-BENZ Official Site
Owner literature, service manuals, technical releases, and plant documentation.
EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
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VCA Certification Portal
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