Audi RS4 B7 Engine Water Coolant Pipe Return Hose Line 4.2 V8 BNS 8E0819373K

Audi RS4 B7 Engine Water Coolant Pipe Return Hose Line 4.2 V8 BNS is an original cooling system component designed specifically for the BNS engine unit. Thanks to its factory-spec fitment, it ensures stable coolant flow and proper return of fluid from the circuit, which translates into safe engine operating temperatures. This used OEM part is a sensible choice when servicing the demanding, high-revving V8 in the RS4 B7.

Specifications and technical data

• SKU: 8E0819373K
• Mark: Audi
• Condition: Used
• OEM Part Number: 8E0819373K
• Substitutable numbers: 8E0819373K, 8E0 819 373 K
• Category: Coolant Hoses

Purpose and function in the cooling system

The offered hose belongs to the Cooling system pipes and hoses category and is responsible for the coolant return in the 4.2 V8 BNS engine circuit of the Audi RS4 B7. A correctly selected return hose:

• stabilizes coolant circulation at high operating temperatures,
• reduces the risk of localized overheating in the area of the V8 heads and block,
• ensures a leak-proof connection between cooling system components.

In the case of high-performance engines such as the RS4 B7, a functional return hose is essential for maintaining an even operating temperature and protecting the unit from thermal damage.

Why it is worth using an original Audi hose

The high-output 4.2 V8 BNS engine requires components with appropriately selected diameter, shape, and flexibility. Using an original Audi hose means:

• a secure fit to the connectors and mounts in the RS4 B7 engine bay,
• preservation of the factory hose routing geometry, which minimizes stress and the risk of abrasion,
• compatibility with other cooling system components without the need for modifications.

As a result, installation is efficient, and the cooling system maintains the parameters specified by the vehicle manufacturer.

Part condition and service application

The hose is a used OEM part, which allows for an economical yet technically correct repair of the cooling system in the Audi RS4 B7. This type of part is particularly suitable in situations where:

• the original hose has cracked, delaminated, or corroded at the clamps,
• a return to the factory cooling system configuration is necessary after engine modifications,
• the priority is to maintain the original manufacturer specification at reasonable service costs.

Selecting a return hose compatible with the RS4 B7 design reduces the risk of leaks and improper system venting.

Thermal safety and cooling system diagnostics

A functional coolant return hose is one of the elements that help maintain a stable engine operating temperature, especially during the dynamic driving typical of RS models. When replacing the hose, it is worth checking other cooling system components – the radiator, thermostat, water pump, and expansion tank.

If you want to better understand the symptoms of engine overheating, common faults, and the impact of individual components on engine longevity, check out the article Engine cooling system – overheating, repair, and used radiators. It is a practical supplement to your knowledge when planning a comprehensive cooling system service.

Expanding your Audi cooling system service

If you are planning a comprehensive repair or upgrade of the engine area in your Audi and need other elements from the same group, such as additional pipes, hoses, or fluid return sections, check out the available parts in the Audi cooling system pipes and hoses category.

Choosing original Audi components within the same part group allows you to maintain the technical consistency of the entire cooling system, which translates into predictable engine behavior across a wide range of loads.