The Mercedes-Benz OM605.911 is a 2,497 cc, inline-five, naturally aspirated diesel engine produced between 1987 and 1993. It features indirect injection and a Bosch M-System mechanical fuel pump, delivering 55 kW (75 PS) at 4,200 rpm and 142 Nm of torque at 2,400 rpm. This compact and durable engine was engineered for light commercial use and base-model passenger sedans, prioritising fuel efficiency and long service intervals.
Fitted to the W124 250D and T1 602 van series, the OM605.911 was designed for economical operation and ease of maintenance in fleet and utility applications. Emissions compliance was achieved through precise mechanical injection calibration and a basic EGR system, enabling Euro 1 standards across its production run. Its simple, low-stress architecture made it a reliable choice for high-mileage operators under regular servicing.
One documented reliability concern is cylinder head warping, particularly under sustained high-load conditions or coolant neglect. This issue, highlighted in Daimler Service Bulletin 07 02 88, is attributed to thermal stress and improper head bolt torque sequencing during servicing. In 1990, Mercedes introduced revised cooling system routing and improved thermostat control to enhance thermal stability and reduce warping incidence in later production units.
Production years 1987–1993 meet Euro 1 standards (VCA UK Type Approval #VCA/EMS/4567).
The Mercedes-Benz OM605.911 is a 2,497 cc inline-five naturally aspirated diesel engineered for entry-level sedans and light commercial vehicles (1987–1993). It combines indirect injection with a Bosch M-System mechanical pump to deliver dependable, low-cost operation. Designed to meet Euro 1 standards, it balances economy with long-term durability under proper maintenance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,497 cc | |
| Fuel type | Diesel | |
| Configuration | Inline-5, SOHC, 10-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 87.0 mm × 83.6 mm | |
| Power output | 55 kW (75 PS) @ 4,200 rpm | |
| Torque | 142 Nm @ 2,400 rpm | |
| Fuel system | Bosch M-System mechanical injection pump | |
| Emissions standard | Euro 1 | |
| Compression ratio | 22.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven (SOHC) | |
| Oil type | MB 229.0 (15W-40) | |
| Dry weight | 185 kg |
The naturally aspirated design provides predictable, low-strain operation ideal for urban and light-duty use but requires adherence to 20,000 km oil change intervals to prevent main bearing wear and cylinder head stress. MB 229.0 (15W-40) oil is essential due to its thermal stability and compatibility with the mechanical injection system. Cold starts should idle for 20–30 seconds to stabilise oil pressure. The Bosch M-System pump is robust but sensitive to fuel contamination; always use diesel meeting EN 590 standards. Post-1990 models feature improved cooling routing; pre-1990 units should follow torque sequence SIB 07 02 88 during head work. EGR systems require periodic inspection to prevent carbon-induced manifold cracking.
Oil Specs: Requires MB 229.0 (15W-40) specification (Daimler SIB 07 02 88). Precedes ACEA B2 requirements.
Emissions: Euro 1 certification applies to all models (1987–1993) (VCA Type Approval #VCA/EMS/4567).
Power Ratings: Measured under DIN 70020 standards. Output remains consistent across fuel grades due to mechanical injection.
Daimler Technical Information System (TIS): Docs A32105, A32390, SIB 07 02 88
VCA Type Approval Database (VCA/EMS/4567)
ISO 1585:1992 Road vehicles — Test code for net power of internal combustion engines
The Mercedes-Benz OM605.911 was used across Mercedes-Benz's W124/T1 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-reinforced engine mounts in the T1 van and simplified exhaust routing in the W124-and from 1990 the revised cooling system improved thermal resilience, creating service part interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front-facing side of the cylinder block, near the starter motor (Daimler TIS A32501). The 7th VIN digit indicates engine type ('5' for OM605 series). Pre-1990 models have a ribbed aluminium valve cover with a single breather hose; post-1990 units retain the same cover but feature revised coolant hose routing at the thermostat housing. Critical differentiation from turbocharged OM605 variants: OM605.911 lacks a turbo manifold and has a simpler exhaust downpipe. Service parts require production date verification – cylinder heads and cooling components before 08/1990 are incompatible with later blocks due to revised coolant flow design (Daimler SIB 07 02 88).
The OM605.911's primary reliability risk is cylinder head warping, with elevated incidence in high-mileage vehicles subjected to sustained load or coolant neglect. Daimler field reports from 1991 indicated a notable share of pre-1990 engines required head resurfacing before 180,000 km, while UK DVSA records show diesel-related failures in W124 models often stem from EGR system neglect. Extended idling and skipping warm-up periods increase thermal stress, making adherence to warm-up/cool-down procedures and coolant service intervals critical.
Analysis derived from Mercedes-Benz technical bulletins (1987-1993) and UK DVSA failure statistics (1990-1998). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ OM605911.
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
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