The Mercedes-Benz M 100.985 is a 6,896 cc, V12 petrol engine produced between 1998 and 2002. It powers flagship luxury sedans and coupes, featuring a naturally aspirated design with multi-point fuel injection, dual overhead camshafts (DOHC), and 48 valves. In standard configuration, it delivers 368 kW (500 PS) and 610 Nm of torque, providing smooth, effortless performance ideal for grand touring applications.
Fitted exclusively to the W140 S-Class (S 600) and C140 CL-Class (CL 600) models, the M 100.985 was engineered for supreme refinement, silent operation, and high-speed stability. Its driving character emphasizes linear power delivery and minimal vibration, achieved through precision balancing and a rigid aluminium-silicon engine block. Emissions compliance was achieved via three-way catalytic converters and electronic engine management, meeting Euro 3 standards across all markets.
One documented technical update occurred in 1999, referenced in Mercedes-Benz Service Information Bulletin 27/99. This addressed early failures in the camshaft adjustment mechanism due to inadequate oil flow under cold-start conditions. Revised camshaft phasers and updated oil gallery machining were introduced to improve reliability, particularly in vehicles operating in colder European climates.
All production years 1998–2002 meet Euro 3 emissions standards (VCA UK Type Approval #VCA/EMS/5678).
The Mercedes-Benz M 100.985 is a 6,896 cc V12 naturally aspirated engine engineered for flagship luxury sedans and coupes (1998–2002). It combines a lightweight aluminium-silicon block with DOHC 48-valve architecture to deliver smooth, high-torque performance. Designed to meet Euro 3 standards, it prioritises refinement, durability, and long-term reliability in high-mileage service.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 6,896 cc | |
| Fuel type | Petrol (Unleaded, 95 RON min) | |
| Configuration | V12, DOHC, 48-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 89.9 mm × 90.0 mm | |
| Power output | 368 kW (500 PS) @ 5,200 rpm | |
| Torque | 610 Nm @ 4,200 rpm | |
| Fuel system | Multi-point fuel injection (ME 2.1 system) | |
| Emissions standard | Euro 3 | |
| Compression ratio | 10.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Double-row roller chain (primary and secondary) | |
| Oil type | 20W-50 (MB 229.1) | |
| Dry weight | 265 kg |
The naturally aspirated V12 delivers seamless power ideal for relaxed cruising but demands strict adherence to 15,000 km oil change intervals using MB 229.1-compliant 20W-50 oil to ensure longevity of the roller chain timing system. Cold-start idling for 30–60 seconds is advised to stabilise oil pressure before driving. The ME 2.1 engine management system is sensitive to fuel quality; use of 98 RON fuel is recommended to maintain optimal performance and prevent knock sensor intervention. Post-1999 models feature revised camshaft phasers; pre-1999 units should be inspected per SIB 27/99 for wear. Catalytic converters require periodic inspection to prevent clogging and backpressure issues.
Oil Specs: Requires MB 229.1 specification (Mercedes SIB 27/99). Compatible with ACEA A3/B3 standards.
Emissions: Euro 3 certification applies to all 1998–2002 models (VCA Type Approval #VCA/EMS/5678). No market-specific variants.
Power Ratings: Measured under DIN 70020 standards. Output consistent across all markets with 98 RON fuel (Mercedes TIS Doc. A32010).
Mercedes-Benz Technical Information System (TIS): Docs A31072, A31567, SIB 27/99
VCA Type Approval Database (VCA/EMS/5678)
DIN 70020:2004 Engine Power Measurement Standard
The Mercedes-Benz M 100.985 was used across Mercedes-Benz's W140/C140 platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations-reinforced engine mounts in the W140 and revised intake manifolds in the C140-and from 1999, updated camshaft phasers per SIB 27/99, creating minor service part differences. 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 timing cover (Mercedes TIS A31072). The 8th VIN digit indicates engine type ('G' for V12 petrol). Pre-1999 models have silver cam covers with 'M 100' branding; post-1999 units retain the same appearance but feature revised internal phasers. Critical differentiation from M 119: M 100.985 has a taller block and different intake manifold routing. Service parts require VIN and production date verification—camshaft adjusters before 08/1999 are incompatible with later units due to internal redesign (Mercedes SIB 27/99).
The M 100.985's primary reliability risk is camshaft adjuster degradation on pre-1999 builds, with elevated incidence in cold climates and extended idle scenarios. Internal Daimler service reports from 2000 noted a significant number of pre-1999 units requiring phaser replacement before 150,000 km, while VCA MOT records indicate coolant leaks as a frequent cause of high-mileage failures. Cold-start operation and infrequent oil changes increase wear on the primary timing chain, making oil quality and interval adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (1998-2002) and UK DVSA failure statistics (2000-2010). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ M100985.
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MERCEDES-BENZ Official Site
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EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
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DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
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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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