Mercedes W211 OM642 Coolant Hose Water Pipe Radiator Expansion Tank A2115011225

Mercedes W211 OM642 Coolant Hose Water Pipe Radiator Expansion Tank is a cooling system component designed for the OM642 diesel engines in the W211 generation E-Class models. It is responsible for the controlled venting of air from the coolant circuit, which promotes stable engine operating temperatures and improves the reliability of the entire system. Thanks to its factory-spec geometry and fitment for the specific engine configuration, it serves as a practical service solution for cooling system repairs and diagnostics.

Specifications and technical data

• SKU: A2115011225
• Mark: Mercedes (Genuine OE)
• Condition: Used
• OEM Part Number: A2115011225
• Substitutable numbers: A2115011225, A 211 501 12 25
• Category: Coolant Hoses

Function in the OM642 cooling system

The vent hose in the OM642 engine cooling system plays a key role in proper fluid circulation. It enables the effective removal of air bubbles from the circuit, which reduces the risk of localized overheating and uneven temperature distribution. A properly functioning hose supports:

• stable operation of the coolant pump,
• even cooling of the cylinder heads and engine block,
• maintenance of proper pressure within the cooling system.

As a result, the OM642 engine in the Mercedes W211 maintains predictable thermal parameters, which translates into longer component life and reduced stress on auxiliary equipment.

Construction and fitment for Mercedes W211

The coolant vent pipe has been designed specifically for the engine bay architecture of the Mercedes E-Class W211 with the OM642 unit. The appropriately selected shape and diameter of the hose facilitate routing it through the tight space of the engine accessories, minimizing the risk of chafing and improper positioning. Precise fitment to factory mounting points allows for installation in accordance with the manufacturer's service documentation.

The item belongs to the Cooling system hoses and pipes group, meaning it works directly with other fluid circuit components – the radiator, thermostat, connectors, and expansion tank. Using a hose with the correct geometry reduces stress on the joints and improves the tightness of the entire system.

Benefits of using the original hose

Choosing a vent hose dedicated to the OM642 in the W211 provides a range of practical service benefits:

• Compatibility with the factory cooling system – no need for modifications or adapting universal hoses.
• Replication of the original hose routing, which facilitates installation and subsequent inspections.
• Better control over the system bleeding process after fluid replacement or repair of other components.

For workshops and users concerned with maintaining correct engine operating parameters, this is a solution that helps reduce the risk of recurring issues related to overheating or air pockets in the system.

Application in service practice

The coolant vent pipe is particularly useful during:

• repairs following cooling system component failure (e.g., leaks, mechanical damage),
• comprehensive periodic maintenance of the OM642 engine,
• diagnostics of overheating problems or unstable operating temperatures.

Maintaining a functional vent hose is especially important in diesel engines, where thermal loads are high and the cooling system operates under significant pressure. Replacing a worn or damaged element with the correct component helps restore proper fluid circulation and facilitates effective bleeding after service.

Technical support and additional information

To better understand the impact of hoses and pipes on engine durability, it is worth checking out the guide on cooling system diagnostics and maintenance – especially in the context of overheating and the use of pre-owned components. Practical tips can be found in the article Engine cooling system – overheating, repair, and used radiators, which discusses, among other things, the importance of proper fluid circulation in popular models.

If you are planning a comprehensive repair or upgrade of the cooling system area in your Mercedes and need other items from the same group, such as return lines, supply hoses, or flexible connecting sections, check the available parts in the Mercedes cooling system hoses and pipes category.

Additional information on the operation and servicing of engine accessories in popular C-Class and E-Class models can be found in the guide Reliability under the star – how to care for engine accessories in popular Mercedes-Benz C-Class and E-Class models?, which helps in making informed choices regarding spare parts and planning service maintenance.