Audi R8 42 Expansion Tank Vent Hose Line Pipe 4.2 FSI 420121107C

Audi R8 42 expansion tank vent hose 4.2 FSI is a specialized component from the Hoses, pipes and tubes category, designed for cooling systems in gasoline-powered vehicles. It is responsible for the stable venting of excess air and vapors from the system, which promotes even engine operation and proper coolant circulation.

Specifications and technical data

• SKU: 420121107C
• Mark: BMW (Genuine OE)
• Condition: Used
• OEM Part Number: 420121107C
• Substitutable numbers: 420121107C, 420 121 107 C
• Fuel type: Petrol
• Part type: Line
• Category: Hoses, Lines & Pipes

Purpose and Function of the Vent Hose

The presented expansion tank vent hose has been designed for precise cooperation with the cooling system of the 4.2 FSI gasoline engine. Its task is to controllably vent air and vapors from the cooling circuit, which helps maintain:

• stable pressure in the cooling system under various engine loads,
• correct fluid level in the expansion tank,
• uniform operating temperature of the power unit.

Thanks to proper venting, the cooling system is less susceptible to localized overheating, and the fluid flow remains more predictable, contributing to a longer lifespan of engine components.

Construction and Fit in the Cooling System

The hose belongs to the group of elements such as hoses, pipes and tubes, which are responsible for the safe transport of fluids and gases in the engine bay. The shape and diameter have been selected to ensure:

• secure medium routing between the expansion tank and other system components,
• appropriate stiffness while maintaining the flexibility necessary during engine operation and body vibrations,
• assembly compatibility with factory brackets and spigots.

Such a fit reduces the risk of leaks, twists, or kinks in the hose, which is crucial for maintaining the sealing of the cooling system and proper venting operation.

Operational Characteristics and Application

The discussed element works with a gasoline-powered engine, where the cooling system operates within a wide range of temperatures and pressures. A properly selected vent hose helps in:

• reducing the accumulation of air bubbles in critical points of the system,
• maintaining a predictable operating temperature during dynamic driving,
• increasing the reliability of the cooling system during prolonged use.

The product comes from the used car parts segment, which allows for an economical replacement of a worn or damaged hose while maintaining structural compatibility with the factory solution.

Benefits of Using the Vent Hose

Replacing a worn component with a properly selected expansion tank vent hose brings a number of practical benefits:

• greater stability of the cooling system operation thanks to proper venting,
• reduced risk of overheating resulting from limiting the presence of air in the circuit,
• better control over the fluid level in the expansion tank,
• preservation of the original system design without the need for modifications.

This solution is particularly beneficial for users who want to maintain their vehicle in a configuration close to the original, while simultaneously reducing service costs.

Other BMW Hoses, Pipes and Tubes and Technical Advice

If you also need other elements from the BMW Hoses, Pipes and Tubes category, check out the BMW hoses, pipes and tubes available in our assortment to select components tailored to your car's specific configuration. For those planning more extensive modifications or vehicle refreshes using second-hand parts, the guide article Car Interior Tuning with Global Parts – How to Use Used Seats and Steering Wheels may be helpful, showing how to sensibly combine functionality with savings.