Repair Services

80A 121 405AQ – Coolant Expansion Tank (World Source)

The Metrix 80A 121 405AQ Tank is a direct-fit OEM-style coolant expansion tank engineered for select Audi Q5 applications. It manages thermal expansion, maintains correct system pressure, and serves as the primary coolant fill point — delivering reliable cooling circuit performance from day one.

$57.00

  • Description
  • Fits These Cars

Description

The 80A121405AQ Coolant Tank by World Source is a direct-fit expansion reservoir designed to restore dependable cooling system performance. Specifically, this tank accommodates the natural thermal expansion and contraction of engine coolant under changing operating temperatures. Furthermore, it maintains essential cooling circuit pressure and provides the primary filling and service point for the entire cooling system.

Supplied by World Source to strict original equipment standards, this replacement reservoir installs directly to factory chassis mounting points and quick-connect hose fittings. Additionally, its precision-molded ports ensure seamless integration with the factory coolant level sensor and return lines without modifications.

Signs Your Expansion Tank Needs Replacing

Inspect your engine compartment for these common failure indicators:

  • A recurring low-coolant warning light on the instrument cluster despite frequent top-offs.

  • Visible hairline stress cracks, crazing, or severe yellowing of the translucent plastic housing.

  • Active coolant weeping or dried crusty residue accumulating around the seam joint or hose necks.

  • Puddles or drips of coolant collecting beneath the engine bay after parking.

  • A distinct sweet coolant odor noticeable under the hood or through the climate vents after driving.

  • Elevated or erratic engine coolant temperature readings caused by air entering the cooling circuit.

Key Features of the 80A121405AQ Coolant Tank

  • OE Part Number: 80A 121 405 AQ

  • Supplier: World Source

  • Function: Regulates coolant expansion volume, maintains operating pressure, and provides system fill access.

  • Material: Virgin high-grade automotive polymer engineered to withstand extreme heat cycles and pressure.

  • Fitment: Direct OEM-specification replacement matching factory mounting tabs and hose connections.

  • Testing: Pressure-tested during manufacturing to ensure verified sealing integrity and long-term durability.

Service Notes

Always verify fitment by VIN before ordering. Never remove the reservoir cap or detach coolant hoses while the engine is hot or pressurized, as escaping steam and fluid can cause severe burns.

Compatibility

Always verify fitment by VIN before ordering. Compatibility depends on chassis generation (including select Audi Q5 platforms), engine code, model year, and the original installed reservoir revision.

Cross Reference

  • 80A 121 405 AQ

  • 80A121405AQ

Year Make Model Engine Notes
2018-2020 Audi Q5
2020-2025 Audi Q5 PHEV