Coolant Hose Connector – 5Q0 122 291AC (OE)

Description

The 5Q0 122 291AC Coolant Connector is the OE right-side cooling system bypass line adapter used on select 2018–2023 Volkswagen and Audi MQB-platform vehicles fitted with a 2.0L turbocharged engine and manual transmission. Positioned on the passenger side of the engine cooling circuit, this T-piece fitting serves as the outlet adapter for the cooling system bypass line — connecting the bypass circuit to the main coolant routing while maintaining sealed, leak-free flow under system pressure. Because VAG engineers designed this connector specifically for the manual transmission cooling circuit layout, it is not interchangeable with the automatic transmission variants of the same connector family.

As part of the upper cooling circuit, the 5Q0 122 291AC coolant connector withstands continuous thermal cycling, coolant pressure, and vibration throughout its service life. Over time, the plastic body can develop hairline cracks — particularly at the outlet port and hose barb connections where stress concentrates. Even a minor fracture at these points causes coolant to bypass the hose connection, triggering low-coolant warnings and, if left unaddressed, progressive coolant loss and the risk of engine overheating. Replacing the failing adapter with a new OE-quality 5Q0 122 291AC connector restores a factory-correct seal and reliable bypass-circuit operation.

Signs Your Cooling System Bypass Connector Needs Replacing

Identifying a failing coolant connector early prevents escalating cooling system damage. Watch for these warning signs:

• Coolant seepage, staining, or dried residue near the right-side cooling circuit connections or along the bypass hose routing

• Recurring low coolant warnings despite topping off, with no obvious external leak elsewhere in the system

• A sweet coolant odor from the engine bay after the engine reaches operating temperature

• Visible cracking, surface crazing, or discoloration on the connector body or port barbs

• A coolant hose that feels loose or fails to seat securely at the adapter port

If any of these symptoms appear, replace the 5Q0 122 291AC coolant connector promptly and pressure-test the cooling system before returning the vehicle to service.

5Q0 122 291AC Coolant Connector — Key Features

• OEM Reference: 5Q0 122 291AC

• OE right-side (passenger-side) cooling system bypass line adapter / T-piece

• Manual transmission applications only — 2.0L engine, 2018–2023 model year range

• Precision-molded housing engineered to OE geometry for correct hose seating and bypass circuit alignment

• Designed to withstand continuous system pressure, elevated coolant temperatures, and thermal cycling

• Compatible with factory-style G12++/G13 coolant chemistry

• Direct-fit replacement — no modifications required

Service Notes for the 5Q0 122 291AC Coolant Connector

• First, confirm the transmission type by VIN before ordering — this connector is specific to manual transmission variants and will not correctly fit automatic transmission applications

• Next, inspect the attached bypass hose for softness, swelling, or cracking; replacing the hose and adapter together at the same service interval is best practice

• Also, replace all hose clamps and O-rings at the adapter ports — reusing old hardware on a new connector can result in an immediate post-installation leak

• Then, refill with the correct VW/Audi-approved coolant (G12++/G13 per your owner’s manual) — never mix coolant types or use unapproved formulations

• Finally, bleed the cooling system completely to eliminate air pockets before returning the vehicle to service; trapped air can cause false temperature readings and heater performance issues

5Q0 122 291AC Coolant Connector — Compatibility & Applications

Always verify fitment by VIN before ordering. Multiple variants may exist within the same model year.

Note: This connector is for manual transmission vehicles only. Automatic transmission variants require a different part number. Always verify by VIN.

Cross Reference Numbers

• 5Q0 122 291AC (VAG OEM — right-side bypass adapter, manual trans)

Additional information