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Ventilation Hose 4K0121109AQ Audi A6 A7 4K C8 3.0 TFSI 55 TFSI
  • Ventilation Hose 4K0121109AQ Audi A6 A7 4K C8 3.0 TFSI 55 TFSI
  • Ventilation Hose 4K0121109AQ Audi A6 A7 4K C8 3.0 TFSI 55 TFSI
Ventilation Hose 4K0121109AQ Audi A6 A7 4K C8 3.0 TFSI 55 TFSI
70,00 zł

Vent Hose / Engine Cooling System Tube – 4K0121109AQ

Original cooling system vent hose (thin overflow tube / coolant vent line to the expansion tank), designed for Audi A7 Sportback (4K / 4K8 generation) and Audi A6 C8 (4K2 / 4K5 / 4KA type) with 3.0 V6 TFSI (55 TFSI designation / EA839 family / DLZA, DKMB and related codes) turbocharged petrol engines based on the modular MLBevo longitudinal platform.

Original VAG cooling system component. Made of specialized hot-pressed polyamide (PA) plastic with enhanced resistance to high temperatures in the inline engine compartment, continuous operating pressure, and direct contact with coolant glycol (G12evo / G13 fluid). It is responsible for continuously venting air bubbles and excess steam pressure from critical areas of the cooling system to the expansion tank, eliminating the risk of steam-air locks in the cylinder heads and protecting the power unit from overheating.

Technical specifications:

  • Catalog part number (OE): 4K0121109AQ / 4K0 121 109 AQ (interchangeable with revision numbers 4K0121109, 4K0121109K, 4K0121109N, 4K0121109AC)

  • System / Category: Engine cooling system (Engine Cooling System / Expansion Tank Vent Line)

  • Function: Cooling vent hose / overflow tube (Coolant Bleeder Hose / Vent Line)

  • Dedicated engine: 3.0 V6 TFSI (55 TFSI / EA839) and related V6 petrol engines on the MLBevo platform

  • Construction: Heat-formed rigid polyamide with factory quick-release connectors (Quick-Connector) and O-ring seals

  • Installation side: Engine compartment – top / front strut tower area, radiator and expansion tank

  • Steering side: Left (LHD – European version) and Right (RHD) – universal component

  • Condition: Original used part (100% functional, leak-tight, unobstructed, plastic in good condition, without microcracks, without signs of heat-induced material degradation, quick-connector sockets intact, locking tabs functional)

  • Manufacturer: Audi AG / VAG (Original OEM)

Main application:

  • Audi:

    • A7 Sportback (type 4K8) – model years 2018 to 2026 (3.0 TFSI / 55 TFSI engines)

    • S7 Sportback (type 4K8) – model years 2019 to 2026 (2.9 TFSI engines)

    • A6 / A6 Avant / Allroad (type 4K2 / 4K5 / 4KA - C8) – model years 2018 to 2026 (3.0 TFSI / 55 TFSI engines)

    • S6 Avant / Saloon (type 4K - C8) – model years 2019 to 2026 (2.9 TFSI engines)

    • A8 / S8 (type 4N2 / 4N8 - D5) – selected versions with 3.0 V6 TFSI engine

    • Q7 / Q8 (type 4M / 4MN) – selected versions with 3.0 TFSI engine

Fitment guarantee and VIN verification

Every hose undergoes a pressure test for leak-tightness and flow, as well as an inspection of the quick-connector sockets before shipping.

Fitment / installation note: The 109 vent hose group has a strictly defined routing geometry in the engine compartment above the front strut tower. The original OEM hose ensures precise engagement with the factory clips and mounting combs without stressing the expansion tank ports. Before purchase, we recommend comparing the full OE number with the index (AQ) on the sticker of the old tube or verifying fitment using the vehicle's VIN.

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