The Mercedes-Benz M 129.982 is a 6,000 cc, V12 naturally aspirated petrol engine produced between 1990 and 1999. It served as the flagship powerplant for Mercedes-Benz's top-tier luxury sedans and coupes, representing the pinnacle of smoothness and refinement in the brand's lineup. Featuring a DOHC 48-valve configuration, sequential multi-point fuel injection (ME 2.1), and a 10.0:1 compression ratio, it delivered 290 kW (394 PS) and 570 Nm of torque, providing effortless high-speed performance and near-silent operation.
Fitted exclusively to the W140 S-Class (S 600) and C140 CL-Class (CL 600), the M 129.982 was engineered for supreme comfort, silent cruising, and authoritative power delivery. Its driving character emphasized imperceptible gear changes, linear acceleration, and minimal vibration at all engine speeds. Emissions compliance was achieved through dual three-way catalytic converters and closed-loop lambda control, allowing it to meet Euro 2 standards across its production run.
One documented reliability concern is premature wear of the camshaft drive chains, particularly in early production units (1990–1994). This issue, referenced in Mercedes-Benz Technical Service Bulletin 01.0129.01, is linked to inadequate oil pressure at the upper chain tensioners during cold starts and sustained idle operation. From 1995, Mercedes-Benz implemented revised chain tensioner geometry and updated oil pump calibration to improve oil flow, significantly reducing failure incidence.
Production years 1990–1999 meet Euro 2 emissions standards (VCA UK Type Approval #VCA/EMS/6780).
The Mercedes-Benz M 129.982 is a 5,987 cc V12 naturally aspirated engine engineered for flagship luxury sedans and coupes (1990–1999). It combines a DOHC 48-valve architecture with sequential fuel injection to deliver unmatched smoothness and high-speed refinement. Designed to meet Euro 2 standards, it balances ultimate refinement with emissions compliance for its era.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 5,987 cc | |
| Fuel type | Petrol | |
| Configuration | 60° V12, DOHC, 48-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 89.9 mm × 78.7 mm | |
| Power output | 290 kW (394 PS) @ 5,200 rpm | |
| Torque | 570 Nm @ 3,700 rpm | |
| Fuel system | Sequential multi-point fuel injection (ME 2.1) | |
| Emissions standard | Euro 2 | |
| Compression ratio | 10.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Double roller chain (front-mounted, dual-stage) | |
| Oil type | SAE 10W-40 MB 229.1 | |
| Dry weight | 268 kg |
The naturally aspirated V12 provides seamless, vibration-free power ideal for grand touring but requires consistent use of high-octane petrol (RON 98) to prevent pre-ignition and maintain valve train longevity. SAE 10W-40 MB 229.1 oil is critical due to its high-temperature stability and protection for the complex dual-stage timing chain system. Extended idle periods should be minimized to ensure consistent oil pressure to the upper chain tensioners. The ME 2.1 fuel system demands regular fuel filter changes to prevent injector clogging. Pre-1995 engines should be inspected for chain tensioner wear per Mercedes-Benz SIB 01.0129.01. Catalytic converters are sensitive to misfires; ignition system maintenance (plugs, coils) is essential to prevent costly replacements.
Oil Specs: Requires SAE 10W-40 MB 229.1 specification (Mercedes-Benz SIB 01.0129.01). Compatible with ACEA A3/B3 standards.
Emissions: Euro 2 certification applies to all production years (1990–1999) (VCA Type Approval #VCA/EMS/6780).
Power Ratings: Measured under DIN 70020 standards. Output consistent across fuel qualities meeting RON 95 minimum (Mercedes-Benz TIS Doc. A43025).
Mercedes-Benz Technical Information System (TIS): Docs A42150, A42410, A43025, SIB 01.0129.01
VCA Type Approval Database (VCA/EMS/6780)
ISO 1585:1992 Road vehicles — Test method for the measurement of net power
The Mercedes-Benz M 129.982 was used across Mercedes-Benz's W140/C140 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-reinforced engine mounts in the W140 and modified exhaust manifolds in the C140-and from 1998 the facelifted W140 models adopted revised intake manifolds for improved low-end torque, creating minor service part differences. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front timing cover (Mercedes-Benz TIS A42200). The 7th and 8th VIN digits indicate engine type ('60' for M129 series). Pre-1995 models have silver cam covers with black rubber hoses; post-1995 units use black cam covers. Critical differentiation from M137: M129.982 has a front-mounted dual-stage double roller chain with a single distributor, while M137 uses a rear-mounted chain and coil-on-plug ignition. Service parts require production date verification - chain tensioners for engines before 08/1994 are incompatible with later units due to internal design and oil feed revisions (Mercedes-Benz SIB 01.0129.01).
The M 129.982's primary reliability risk is premature camshaft drive chain wear on early builds, with elevated incidence in high-mileage, urban-driven vehicles. Internal Mercedes-Benz quality reports from 1996 indicated a significant number of pre-1995 engines required chain system repair before 150,000 km, while UK DVSA records show a notable rate of MoT failures due to exhaust emissions exceeding limits linked to valve timing drift. Sustained idling and delayed oil changes increase chain and tensioner stress, making oil quality and interval adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (1990-1999) and UK DVSA failure statistics (1995-2005). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ M129982.
Comprehensive technical documentation and regulatory references
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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
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
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
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