Audi A6 C7 A7 4G Water Coolant Expansion Tank Reservoir 1.8 TFSI 4G0121403AE

The Audi A6 C7 Coolant Expansion Tank is a component of the cooling system responsible for safely managing and storing excess coolant during engine operation. This offered tank, from the original Audi line, ensures proper circulation and a stable coolant level, contributing to predictable engine performance. It's a practical solution for users seeking a proven component for a service replacement in their Audi A6 C7 generation.

Specifications and technical data

• SKU: 4G0121403AE
• Mark: Audi
• Condition: Used
• OEM Part Number: 4G0121403G
• Substitutable numbers: 4G0121403G, 4G0 121 403 G
• Category: Expansion & Overflow Tanks

Purpose and Function in the Cooling System

The presented expansion tank is designed to work with the cooling system in the Audi A6 C7, where it compensates for changes in coolant volume and maintains stable operating pressure. A correctly chosen tank helps reduce the risk of engine overheating, facilitates system bleeding, and allows for visual coolant level checks. Thanks to its factory-designed hose connections and mounting points, the component integrates with cooling hoses and accessories as intended by the manufacturer.

Original Origin and Identification Parameters

This item belongs to the Expansion Tanks category and is part of Audi's original cooling system. The product has a dedicated OEM part number and assigned reference numbers, which simplifies unambiguous identification in service catalogs and when selecting a replacement. The technical description also includes data such as the SKU, OEM Part Number, associated Reference Numbers, as well as the Brand and Condition, allowing for quick verification of compatibility with a specific vehicle configuration.

Item Condition and Service Application

The offered tank is a used component, primarily intended for service applications in vehicles where the original tank has become worn, cracked, or is leaking. Replacing it with an original part from a dismantled vehicle allows for maintaining factory fitment while reducing repair costs compared to a new part. This solution is particularly beneficial for comprehensive cooling system work, such as replacing hoses, the radiator, or the thermostat, where component consistency is important.

Benefits of Using an Original Expansion Tank

Using an original expansion tank in an Audi A6 C7 ensures:

• factory fitment to cooling system mounts and hoses,
• maintenance of the manufacturer's specified working capacity of the tank,
• proper interaction with the pressure cap and level sensors (if present in the specific configuration),
• material compatibility with other cooling system components. This makes it easier to maintain stable engine operating temperature and reduces the risk of failures due to incorrect part selection.

Expanding Audi Cooling System Service

If you are planning a comprehensive repair or upgrade of the engine area in your Audi and need other parts from the same group, such as additional tanks, mounting elements, or related cooling system components, check the available parts in the Audi Expansion Tanks category. When planning broader service work, it's also worth analyzing the strategy for selecting used and new parts in the context of operating costs. A comparison of different solutions used in popular engine units might be helpful – you can find more information in the article Volkswagen 1.9 TDI vs 1.4 TSI – Engine Evolution and Repair Costs, which shows how to optimize expenses using parts from the secondary market.