Removing and installing heat exchanger: Audi A8 D4

🧭 Before you start

Fits: Audi A8 D4 (4H, 2010–2017)

• Opens: coolant

Don't miss

• To stop coolant running into the plenum chamber on detaching the coolant hoses (A) and (B).
• Mark the connector (F) (risk of interchange) and unplug from the left footwell flap control motor V108 (if this control motor has not been removed).
• If the heat exchanger has already been replaced, a holder (E) and the bolt (F) will have been fitted in place of the webs (A).
• Removal of this holder involves taking out the control motors V107, V110 and V299.
• On inserting the heat exchanger (A), take care not to damage the two connections (B) and the two coolant pipes (D) and (E).

🔩 Torque settings

Values can differ between engine variants — check the code stamped on your block.

ℹ️ Always cross-check the exact figure against your vehicle's factory manual before final tightening — a wrong torque can damage the engine. These values are extracted from workshop data and may not cover every variant or revision.

📋 Procedure

1. ⚠ 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.
2. Perform preparations for removing heat exchanger .
3. Mark the layout of the coolant hoses at the connections to the heat exchanger (A) (supply from coolant circulation pump V50) and (B) (return to engine). [Note: This illustration shows the arrangement of the coolant hoses on a vehicle with a rear air conditioning unit and an auxiliary heater. Vehicles with no "“rear air conditioning unit”" optional extra are not fitted with the coolant hoses (D) and (F) for example Incorporation of air conditioner into coolant circuit.The heat exchanger(s) is/are installed in the air conditioning units such that a certain coolant flow direction is required for proper bleeding of the heat exchanger. The coolant hoses must therefore be connected in the correct positions Incorporation of air conditioner into coolant circuit.Bleed coolant circuit and 19Cooling system/coolant; Draining and filling cooling system.]
4. Use hose clamps (J) to pinch off the coolant hoses (C) and (B).
5. If fitted, pinch off the coolant hose (D) with a hose clamp (J) (vehicles with rear air conditioning unit).

6. Cover area beneath connections for coolant hoses (A) and (B) in plenum chamber e.g. with absorbent paper.
7. Place a small container under the connections for the coolant hoses (A) and (B) (to the heat exchanger). [Note: To stop coolant running into the plenum chamber on detaching the coolant hoses (A) and (B).]
8. Detach coolant hoses (A) and (B) from connections to heat exchanger of air conditioning unit.
9. Attach a section of tubing ((A) and (C)) to each of the two connections to the heat exchanger.
10. Place a vessel (B) beneath the other end of the hose (C).
11. Use a compressed air gun (D) to carefully blow the coolant via the hose (A) out of the heat exchanger (in the direction opposite to normal coolant flow) into the vessel (B).
12. Protect floor covering and centre tunnel beneath heat exchanger (A) with impermeable sheeting and absorbent paper.
13. Mark the connector (F) (risk of interchange) and unplug from the left footwell flap control motor V108 (if this control motor has not been removed).
14. Fix the wiring harness (G) in position at the air conditioning unit such that it does not impede removal of the heat exchanger (A).
15. Detach the clamps (B) and (C) from the connections at the heat exchanger (A). [Note: At the start of production, screw-type clamps were fitted at the connections at the heat exchanger (A). This illustration shows a version with plastic clamps (B) and (C), introduction of which has not yet been finalised.At the start of production, the coolant pipes (B) to the heat exchanger were not fitted with plastic clamps (A), but rather with screw-type clamps (metal clamps).]
16. Remove the bolt (A) at the clamps (B) for the coolant pipes (C) and (D).
17. Detach the clamps (B).
18. Use a screwdriver (C) for example to unfasten and detach the plastic clamps (A).
19. Completely remove the two webs (A) (on the right of the air conditioning unit). [Note: If the heat exchanger has already been replaced, a holder (E) and the bolt (F) will have been fitted in place of the webs (A).]
20. Place a vessel beneath the connection for the coolant pipe (D) at the heat exchanger (A).
21. Unfasten the two coolant pipes (D) and (E) from the connections of the heat exchanger (A) and carefully swivel aside.
22. Remove the heat exchanger (A) in arrow direction (arrow) from the air conditioning unit into the passenger's footwell. [Note: Depending on the version, it may not be possible to remove the heat exchanger (A) in the direction of (arrow) on vehicles manufactured at the start of production (model year 2010). If this is the case, the heat exchanger must be removed in the direction of the driver's footwell.]
23. Remove steering column and foot controls Running gear, axles, steering48Steering column; Removing and installing steering column and Brake system46Brake pedal; Exploded view - brake pedal.
24. ⚠ The air conditioner will not function properly if control motors and/or the corresponding connectors are interchanged Overview of control motors of air conditioner.The control motors and connectors are identical. If these are incorrectly installed or connected, the corresponding flaps can no longer be properly matched and/or activated.Mark control motors and connectors clearly before detaching or removing to prevent incorrect installation. — Remove the holder for the control motors V110 and V299Removing and installing holder for control motor V110 and V299. [Note: Removal of this holder involves taking out the control motors V107, V110 and V299.]
25. Remove the holder for the control motors V108 and V411Removing and installing holder for control motor V108 and V411. [Note: To remove the heat exchanger it is not absolutely essential to take out the holder for the control motors V108 and V411. Removal of this holder is however advisable in the interests of greater accessibility and to provide more room.Removal of this holder involves taking out the control motors V108 and V411.]
26. Remove the heat exchanger (A) in the direction opposite to that of the arrow (arrow) into the driver's footwell.
27. Check the seals (B) attached to the heat exchanger (A). Only install a heat exchanger if the seals are in perfect condition and firmly affixed. [Note: A seal (B) may curl up on insertion if not correctly bonded on.If a seal (B) is damaged or not correctly fitted, cold air may flow past the heat exchanger and lead to problems with cold air emerging from the air conditioning unit or noise.]
28. Check the two connections (C) of the heat exchanger (A) for damage or contamination.
29. Check the air conditioning unit for contamination by way of the mounting slot (C) (slot for heat exchanger) and, if applicable, the mounting slot (D) for the auxiliary air heater element Z35 (vehicles with diesel engine only).
30. Remove any dirt or remnants of escaped coolant from the air conditioning unit (e.g. after removing a leaking heat exchanger).
31. Check for any edges or projecting material at the mounting slot (C) at the top and bottom on either side of the air conditioning unit.
32. Remove any residual material left at the separation points during manufacture of the air conditioning unit and smooth off any edges. [Note: Edges may be produced at the separation points when manufacturing the air conditioning unit or projecting material may be left in the air conditioning unit. The connections for the coolant pipes at the heat exchanger could be damaged at these locations on installation.]
33. Carefully slide home the heat exchanger (B) in the air conditioning unit. [Note: On inserting the heat exchanger (A), take care not to damage the two connections (B) and the two coolant pipes (D) and (E).]
34. Fit the holder (E) and the bolt (F). [Note: The holder (E) and the bolt (F) are available as replacement parts Electronic parts catalogue.On vehicles on which the heat exchanger (A) was removed into the driver's footwell, slide home the heat exchanger (A) in arrow direction (arrow) in the air conditioning unit.]
35. Moisten the two connections (B) of the heat exchanger (A) with a small quantity of coolant or lubricate with silicone grease. [Note: Silicone grease is available as a replacement part: part number G 000 405 A2 Electronic parts catalogue.]
36. Check the connection area for the two coolant pipes (D) and (E) to the heat exchanger for damage or contamination.
37. Moisten the new seals (C) (included in the scope of delivery of the heat exchanger) with a small quantity of coolant (or lubricate slightly with silicone grease).
38. Attach the new seals (C) to the two coolant pipes (D) and (E).
39. Insert the two coolant pipes (D) and (E) with the corresponding seal (C) in the connections of the heat exchanger (B) and press home. [Note: Do not cant coolant pipes (D) and (E) when pressing them into the heat exchanger connections.]
40. Check the position of the seals (C) between the coolant pipes (D) and (E) in the connections (B) of the heat exchanger (A).
41. ⚠ Seals (C) that are not fitted correctly or are crushed can cause leaks.The seals (C) must be inserted completely in the connections in the connecting flange (B) with the coolant pipes (D) and (E) — Remove the bolt (B) from the new clamps (A).
42. Remove the bolt (A) at the clamps (B) for the coolant pipes (C) and (D).
43. Attach the new clamps (B) to the coolant pipes (C) and (D) and turn the clamps (B) such that the bolt (A) can be fitted.
44. Consecutively press the coolant pipes (C) and (D) into the heat exchanger and attach one clamp (B) each at the joint to the heat exchanger as shown. [Note: The clip (B) engages on being pressed together.]
45. Screw one bolt (A) into each of the clamps and secure the clamp (B) by tightening the bolt (A) (bolt tightening torque 2 Nm). — 2 Nm (1.5 lb-ft)
46. Check that the clamps (B) are properly positioned on the connections of the heat exchanger and coolant pipes.
47. Check the installation position of the clamps (B) and the bolts (A). They must not make contact with the air conditioning unit or other components. [Note: Not available at present (introduction not yet finalised). Until further notice, screw-type clamps (metal clamps) will be supplied as replacements Electronic parts catalogue.]
48. Attach the new plastic clamps (F) (if contained in the scope of delivery of the heat exchanger) to the coolant pipes (D) and (E).
49. ⚠ Plastic clamps (F) are not to be re-used.Always fit new clamps (F)Electronic parts catalogue. — Attach the plastic clamps (F) as shown at the joints between the heat exchanger and the coolant pipes (D) and (E) and press together. [Note: The clamp (F) engages on being pressed together.]
50. Check for correct positioning and proper engagement of the clamps (F) at the coolant pipes (D) and (E).
51. Check that grommet (H) is correctly positioned in back wall of plenum chamber.
52. Properly connect coolant hoses to heat exchanger, paying attention to markings.
53. Attach the coolant hose (A) to the coolant pipe to the heat exchanger (heed the marking) and secure it with a clamp.
54. Fit the coolant hose to the heat exchanger (B) onto the coolant pipe such that air can still escape on bleeding the coolant circuit (do not press fully on).
55. Detach the hose clamp (J) from the coolant hose (C).
56. Add coolant to coolant expansion tank 19Cooling system/coolant; draining and adding coolant.
57. Screw the hand pump of the cooling system testerV.A.G 1274/ to the filler neck of the coolant expansion tank.
58. Using e.g. hand pump of cooling system testerV.A.G 1274/, carefully press coolant out of coolant expansion tank into heat exchanger.
59. As soon as coolant emerges from the joint between the coolant hose (B) and the coolant pipe from the heat exchanger, press the coolant hose (B) fully onto the coolant pipe.
60. Secure the coolant hose (B) with a clamp.

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