Mercedes W204 C207 W212 W205 W213 M274 Petrol Belt Tensioner A2742000870

Mercedes W204 C207 W212 W205 W213 M274 Petrol Belt Tensioner is an original component from the Tensioner and Idler Pulleys group, designed for M274 petrol engines in popular Mercedes C-Class and E-Class models. It ensures stable operation of the accessory belt, which translates into reliable performance of the alternator, pump, and other belt-driven components.

Specifications and technical data

• SKU: A2742000870
• Mark: Mercedes (Genuine OE)
• Condition: Used
• OEM Part Number: A2742000870
• Substitutable numbers: A2742000870, A 274 200 08 70
• Fuel type: Petrol
• Category: Idlers & Tensioners

Purpose and function of the belt tensioner

The belt tensioner in M274 units is responsible for maintaining the proper tension of the accessory belt in the petrol engine. A correctly selected component reduces slippage, noise, and uneven operation of the accessories, which is important for both driving comfort and the durability of the entire drive system.

For Mercedes W204, C207, W212, W205, and W213 models, using the appropriate tensioner is crucial for maintaining correct belt routing geometry and stable engine operation across the full load range.

Construction and technical characteristics

The tensioner from the Tensioner and Idler Pulleys group operates continuously, compensating for load changes and belt stretching during operation. The design provided by the vehicle manufacturer ensures:

• properly selected pressure force on the accessory belt,
• stable belt guidance at variable rotational speeds,
• reduction of vibrations transmitted to engine accessories,
• compatibility with the M274 petrol engine drive system.

Thanks to this, the charging system, air conditioning, and other belt-driven elements can operate under predictable conditions, which promotes their longer service life.

Application in M274 petrol engines

The presented tensioner is designed for petrol units, where precise belt tension is of particular importance at higher rotational speeds and during dynamic driving. A correctly selected component minimizes the risk of:

• the accessory belt slipping off or jumping,
• excessive wear of the belt edges,
• the occurrence of unwanted noises in the engine compartment.

For workshops and users, this means more predictable operation and a lower risk of failures related to the accessory drive system.

Benefits of choosing an original Mercedes component

Choosing a tensioner dedicated to specific Mercedes C-Class and E-Class models with the M274 engine primarily means reliable fitment to the factory system. Original geometry and operating parameters facilitate installation and limit the need for additional adjustments after replacement.

The component from this group is particularly recommended for professional repairs, where operational predictability, compliance with service documentation, and seamless cooperation with other drive system components are essential.

Accessory drive system repair and part selection

If you are planning a comprehensive repair or upgrade of the engine area in your Mercedes and need other elements from the same group, such as additional guide pulleys, idler pulleys, or other tensioners, check the available parts in the Mercedes Tensioner and Idler Pulleys category.

For workshops that want to reduce vehicle downtime and use readily available original components, an article describing the impact of the availability of used OEM parts on repair time may be useful – more information can be found in the material: Availability of car parts on the spot vs. repair time – how do used OEM parts shorten the stay in the workshop?.