Mercedes SLK R170 Coolant Expansion Overflow Tank Reservoir Bottle A1705000249

Mercedes SLK R170 Coolant Expansion Overflow Tank Reservoir Bottle is an original cooling system component designed for stable engine operation under demanding conditions. As part of the Expansion tanks group, it ensures coolant level control, expansion compensation, and safe discharge of excess fluid, which translates into predictable and smooth operation of the power unit. This used OEM component is a sensible choice for servicing older SLK R170 models, where structural fit and proper integration with the factory cooling system are essential.

Specifications and technical data

• SKU: A1705000249
• Mark: Mercedes (Genuine OE)
• Condition: Used
• OEM Part Number: A1705000249
• Substitutable numbers: A1705000249, A 170 500 02 49, A1705000049, A 170 500 00 49, A1245000406, A 124 500 04 06
• Category: Expansion & Overflow Tanks

Purpose and function in the cooling system

The presented expansion tank is a cooling system component responsible for buffering changes in coolant volume and maintaining stable operating pressure. In practice, this means:

• compensation for the thermal expansion of the fluid during engine heating and cooling,
• safe collection of excess fluid that does not fit in the main circuit,
• easier visual monitoring of the fluid level in the engine bay,
• reduction of the risk of overheating resulting from air in the system.

Thanks to its factory fit for the SLK R170 design, the tank works with original hoses, mounts, and the cap, which facilitates trouble-free installation and maintains the serial operating parameters of the cooling system.

Original origin and compatibility with Mercedes SLK R170

As a Mercedes brand product from the OEM group, the expansion tank was designed specifically for the engine bay geometry of the SLK R170 model. This means:

• maintaining the factory mounting position relative to the engine and radiator,
• correct routing of connection ports relative to coolant hoses,
• compatibility with serial brackets and supports in the bodywork.

Such a fit reduces the need for modifications, minimizes the risk of leaks, and facilitates future service. The original expansion tank also ensures predictable material behavior over a long period of operation, in accordance with the vehicle manufacturer's specifications.

Characteristics of the used component

The offered tank comes from a used vehicle, which in practice means that it is a part with a history of use, but still suitable for further service after verifying its condition. For plastic components such as expansion tanks, it is important to maintain:

• tightness of the body and connection ports,
• shape stability under operating temperature conditions,
• correct geometry of mounting points.

Choosing a used OEM component is often a beneficial compromise between repair costs and maintaining the original technical specifications of the vehicle, especially in the case of older model generations where the availability of new parts may be limited.

Benefits of using an original expansion tank

Using a factory expansion tank in a Mercedes SLK R170 translates into a number of practical service and operational benefits:

• Stable cooling system operation – proper pressure and fluid volume compensation reduces the risk of overheating and air pockets.
• Factory fit – no need to adapt hoses, brackets, or mounts, which shortens installation time.
• Consistency with other system elements – maintaining the original engineering concept of the vehicle manufacturer.

This approach is particularly important in roadster-type cars, where the cooling system often operates in varied thermal and aerodynamic conditions.

Cooling system service expansion and related parts

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 tanks, mounting elements, or related cooling system components, check the available parts in the Mercedes Expansion tanks category.

For drivers interested in a broader perspective on diesel engine operation and the impact of aftermarket parts availability on vehicle maintenance costs, the article comparing popular BMW engines may be helpful – you can find it here: BMW N47 vs M57 / M57N / M57N2 – ranking of legendary diesels.