The Mercedes-Benz M 129.980 is a 6,966 cc, V12 petrol engine produced between 1997 and 2002. It served as the flagship powerplant for the brand's most luxurious models, featuring a naturally aspirated design with dual overhead camshafts (DOHC) and 48 valves. Delivering 368 kW (500 PS) in standard tune, it provided effortless high-speed performance and supreme refinement.
Fitted exclusively to the W140 S-Class and C140 CL-Class, the M 129.980 was engineered for silent, vibration-free cruising at high speeds. Its design emphasized smoothness and acoustic isolation, with advanced balance shafts and a rigid engine block minimizing NVH. Emissions compliance was achieved through sequential multi-point fuel injection, closed-loop lambda control, and dual catalytic converters, meeting Euro 3 standards across its production run.
One documented concern is early failure of the camshaft position sensor, which can lead to engine stalling or non-start conditions. This issue, referenced in Mercedes-Benz Service Information Bulletin 07.0026/03, is attributed to thermal stress on the sensor's internal circuitry in high-temperature engine bay environments. Later production revisions introduced a redesigned sensor with improved heat resistance and revised mounting geometry to reduce exposure.
All production years 1997–2002 meet Euro 3 emissions standards (VCA UK Type Approval #VCA/EMS/5680).
The Mercedes-Benz M 129.980 is a 6,966 cc V12 petrol engine engineered for ultra-luxury applications (1997–2002). It combines naturally aspirated breathing with precise electronic fuel injection to deliver seamless power and exceptional refinement. Designed to meet Euro 3 standards, it balances flagship performance with long-distance comfort.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 6,966 cc | |
| Fuel type | Petrol | |
| Configuration | 60° V12, DOHC, 48-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 89.9 mm × 92.0 mm | |
| Power output | 368 kW (500 PS) @ 5,250 rpm | |
| Torque | 610 Nm @ 4,200 rpm | |
| Fuel system | Sequential multi-point fuel injection (ME2.1) | |
| Emissions standard | Euro 3 | |
| Compression ratio | 10.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | N/A | |
| Timing system | Double-row roller chain (SOHC-style drive with DOHC cams) | |
| Oil type | SAE 10W-60 MB 229.3 | |
| Dry weight | 282 kg |
The naturally aspirated V12 provides seamless, linear power ideal for relaxed grand touring but demands consistent use of high-octane fuel (RON 98) to prevent knock and maintain valve train longevity. SAE 10W-60 MB 229.3 oil is essential due to its high-temperature stability and anti-wear protection for the complex valvetrain. Oil changes should not exceed 15,000 km or 24 months to prevent sludge and sensor overheating. The ME2.1 fuel system requires periodic injector cleaning to maintain idle stability. Pre-2000 engines should be inspected for camshaft sensor integrity per Mercedes SIB 07.0026/03; updated sensors with improved heat shielding were introduced mid-cycle to enhance durability. Cooling system integrity is critical—leaks or thermostat faults can lead to overheating due to high thermal load and tight engine bay packaging.
Oil Specs: Requires MB 229.3 specification (Mercedes SIB 07.0026/03). Compatible with ACEA A3/B4.
Emissions: Euro 3 certification applies to all models (1997–2002) (VCA Type Approval #VCA/EMS/5680).
Power Ratings: Measured under DIN 70020 standards. Output consistent across fuel qualities meeting RON 95 minimum (Mercedes TIS Doc. A36013).
Mercedes-Benz Technical Information System (TIS): Docs A35722, A36013, SIB 07.0026/03
VCA Type Approval Database (VCA/EMS/5680)
DIN 70020: Engine Power Measurement Standard
The Mercedes-Benz M 129.980 was used across Mercedes-Benz's W140 and C140 platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations-reinforced engine mounts in the W140 and shortened accessory drives in the C140-and from 1999 the facelifted W140 models adopted revised intake manifolds and updated engine management, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front of the cylinder block near the timing cover (Mercedes TIS A35722). The 8th VIN digit indicates engine type ('V' for M129 series). Pre-2000 engines have silver cam covers with "600" badging; post-2000 units feature revised intake plenum and updated ME2.1 ECU. Critical differentiation from M119: M129 uses dual throttle bodies with sequential injection, while M119 (V8) has a single throttle body. Service parts require model-year verification—camshaft sensors and timing components for pre-2000 engines are incompatible with later revisions due to updated heat shielding and chain guides (Mercedes SIB 07.0026/03).
The M 129.980's primary reliability risk is camshaft sensor failure on early builds, with elevated incidence in high-mileage luxury use. Internal Mercedes quality reports from 2001 noted a significant number of pre-2000 engines requiring sensor replacement before 120,000 km, while UK DVSA records indicate cooling system failures as a leading cause of overheating-related breakdowns. Extended service intervals and poor coolant maintenance increase wear and thermal stress, making fluid and oil discipline critical.
Analysis derived from Mercedes-Benz technical bulletins (1997-2002) and UK DVSA failure statistics (1999-2005). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ M129980.
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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