Removing and installing heater coolant shut-off valve N279 — AUDI

🧭 Before you start

Fits: Audi A8 D4 (4H, 2010–2017)

📋 Procedure

1. Switch off ignition (and auxiliary heater).
2. Remove the plenum chamber cover General body repairs, exterior50Bulkhead; Removing and installing plenum chamber cover.
3. Remove fresh air intake .
4. ⚠ Danger of scalding from hot steam or hot coolant.The cooling system is pressurised when the engine is warm.To relieve pressure, cover coolant expansion tank cap with a cloth and open carefully. — Open cap (arrow) on coolant expansion tank.
5. Use an absorbent cloth or absorbent paper to cover area beneath N279(A).

6. Mark positions of coolant hoses (C), (D) and (E) at N279(A). [Note: There are different versions of N279 (with 3 or 4 connections for coolant hoses). On the version with 4 connections, one connection is sealed with a cap (H).Depending on the model and the engine, the vehicle may additionally be fitted with a non-return valve in the coolant circuit. A certain amount of coolant in the small circuit flows back to the engine via this non-return valve in the small circuit even when the N279 is activated 19Cooling system/coolant; Connection diagram - coolant hoses.]
7. ⚠ Ensure that coolant hoses (C), (D) and (E) are positioned correctly at N279(A).If coolant hoses are interchanged, this can cause the heating in the passenger compartment to fail. — Clamp off coolant hoses (C), (D) and (E) in area of N279(A) (e.g. with hose clamps up to dia. 25 mm3094).
8. Unfasten clamps and detach coolant hoses (C), (D) and (E).
9. Unplug electrical connector (B) from N279(A).
10. Remove securing bolts (F) from N279(A).
11. Remove N279.
12. Butt-joint coolant hoses (C), (D) and (E).
13. Bleed coolant circuit; observe notes .
14. If applicable, check activation and operation of N279 in "“Guided Fault Finding”" mode.
15. Re-install remaining components (removed earlier).

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