BSNOVT Radiator Overflow Hose Coolant Bypass Line for Audi A4/A5 2017–2021 — Direct OEM Fit 8W0121081AN, Heat-Resistant

BSNOVT Radiator Overflow Hose is a direct replacement coolant bypass line built to replace OEM 8W0121081AN for select Audi A4 and A5 models, channeling excess coolant to the expansion tank to protect engine temperature balance.

Designed for Audi owners and mechanics who need a reliable coolant transfer line, this BSNOVT hose restores proper overflow flow and helps maintain the cooling system’s integrity after the original line fails or is removed. Built from heat-resistant materials, the hose fits specific Audi A4 and A5 variants and arrives ready to install as a single-piece replacement.

Which Audi models does this overflow hose fit?

This BSNOVT radiator overflow hose is made to match the fitment and routing of the original amplifier for certain 2017–2021 Audi A4 and A5 vehicles. Confirm compatibility with your VIN or service manual before purchase to ensure correct fit and performance.

• Compatible with Audi A4 (2017–2020) and A4 Quattro (2017–2021)
• Fits Audi A4 allroad (2017–2020)
• Fits Audi A5 Quattro and A5 Sportback (2018–2020)

How does this hose replace OEM part 8W0121081AN?

The BSNOVT line is manufactured to replicate the OEM part’s shape, ports, and attachment points so it installs in the same routing as the original. That ensures a snug connection to the expansion tank and radiator system without need for aftermarket adapters.

• Direct replacement for part number 8W0121081AN
• Same connection points and contours as the original component
• Ships as a single hose ready for straightforward swap-in installation

What materials and durability can I expect?

Constructed from high-temperature-resistant elastomers and reinforced sections, this coolant transfer line resists engine-bay heat and typical coolant exposure. The material selection aims to reduce swelling, softening, and premature cracking under normal operating conditions.

• Heat-resistant compound suitable for engine bay temperatures
• Reinforced areas to resist pressure and flexing
• Designed to minimize leaks and extend service life

How easy is installation and what’s included?

The product ships as one replacement hose so a mechanic or experienced DIYer can replace the old line without sourcing extra fittings. Basic tools are usually all that’s required and the hose follows the OEM routing for a clean install.

• Includes one BSNOVT coolant overflow/bypass hose
• Direct-fit design to speed installation time
• No additional parts typically required—check clamps and seals during replacement

Who is this for: This BSNOVT radiator overflow hose is intended for Audi A4 and A5 owners, independent repair shops, and DIY enthusiasts who need a dependable OEM-style replacement for part 8W0121081AN. Choose this hose if you want a heat-resistant, direct-fit coolant bypass line that restores proper overflow routing and helps prevent coolant loss after the original line becomes compromised.