Removing, installing and tensioning toothed belt: Audi A6 C5 (ALT, AMB, AVJ, BEX, …)

🧭 Before you start

Fits: Audi A6 C5 (4B)

• Timing position: the crankshaft or camshaft is set and locked during this job

Don't miss

• Before removing, mark direction of rotation of poly V-belt with chalk or felt-tip pen. If the belt runs in the opposite direction when it is refitted, this can cause breakage.
• The engine must only be turned at the crankshaft, in the direction of normal engine rotation (clockwise). — Rotate crankshaft to TDC by turning bolt for toothed belt sprocket.
• Do not to bend limit stop (A) of eccentric adjuster.
• Mark direction of rotation of toothed belt with chalk or felt-tip pen.
• Fit toothed belt onto crankshaft sprocket, noting direction of rotation.

🔧 Engine codes this applies to

🔩 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.

📐 52 workshop diagrams for ALT

Real factory drawings for this job — timing marks, bolt locations and routing. Locked in the free view.

📋 Procedure

1. Vehicles with auxiliary heater: remove bolts (arrows) securing exhaust pipe for auxiliary/additional heater to noise insulation.
2. Release fasteners (1 ... 3) and (5) and take off front noise insulation.
3. Remove front bumper cover General body repairs, exterior63.
4. Move lock carrier into its service position General body repairs, exterior50.
5. Lift off engine cover (arrows). [Note: Before removing, mark direction of rotation of poly V-belt with chalk or felt-tip pen. If the belt runs in the opposite direction when it is refitted, this can cause breakage.]

6. Turn the tensioner in the direction of the (arrow) to slacken the poly V-belt.
7. Remove poly V-belt and release pressure from the tensioner.
8. Unscrew bolts (arrows) and remove poly V-belt tensioner.
9. Remove toothed belt cover (top section) (arrows).
10. ⚠ The engine must only be turned at the crankshaft, in the direction of normal engine rotation (clockwise). — Rotate crankshaft to TDC by turning bolt for toothed belt sprocket.
11. Unscrew vibration damper and remove.
12. Remove toothed belt cover (centre and bottom) (arrows).
13. ⚠ The toothed belt tensioner is oil-damped and can therefore only be compressed slowly by applying constant pressure.To avoid damage, do not apply more force than necessary when compressing the toothed belt tensioner. — Applying constant and moderate force, use hexagon key to press toothed belt tensioner anti-clockwise in direction of (arrow) until piston of tensioner can be locked with locking plate T10008.
14. Insert locking plate T10008 and make sure that it remains in place. [Note: Do not to bend limit stop (A) of eccentric adjuster.]
15. To slacken toothed belt, loosen nut (1) on tensioning roller and turn eccentric adjuster clockwise (arrow) using pin wrench3387.
16. Loosen nut (1) to slacken toothed belt.
17. Mark direction of rotation of toothed belt with chalk or felt-tip pen.
18. Remove toothed belt. [Note: The toothed belt adjustment must also be performed as described below, even if the toothed belt has only been removed from the camshaft sprocket.The crankshaft must not be at TDC at any cylinder when the camshaft is turned. Otherwise, there is a risk of damage to valves and piston crowns.]
19. Fit toothed belt onto crankshaft sprocket, noting direction of rotation.
20. Install bottom toothed belt cover. [Note: The vibration damper/ pulley can only be installed in one position: The hole (arrow) in the vibration damper must fit over the projection on the toothed belt sprocket on the crankshaft.]
21. Secure vibration damper/ pulley. Note positive location (arrow).
22. Align markings on camshaft sprocket / cylinder head cover and markings on vibration damper / toothed belt cover (arrows).
23. Make sure that toothed belt tensioner is still locked with locking plate T10008.
24. Fit toothed belt onto coolant pump, then tensioning roller, and finally camshaft sprocket. [Note: Do not to bend limit stop (A) of eccentric adjuster.]
25. Turn eccentric adjuster anti-clockwise onto stop in direction of (arrow) using pin wrench3387.
26. Hold eccentric adjuster in this position and pull out locking plate T10008.
27. Turn eccentric adjuster clockwise in direction of (arrow) until gauge (2) with dimension (a) = 8 mm (e.g. drill bit) can be pulled through between tensioning lever and housing of tensioner.
28. Hold eccentric adjuster in this position and tighten nut (1) of tensioning roller to 27 Nm. — 27 Nm (20 lb-ft)
29. ⚠ The engine must only be turned at the crankshaft, in the direction of normal engine rotation (clockwise). — Turn crankshaft two rotations via securing bolt for toothed belt sprocket until it is positioned at TDC again.
30. Use gauge (2) (e.g. drill bit) to check dimension (a) between tensioning lever and housing of tensioner.
31. ⚠ The toothed belt tensioner is oil-damped and can therefore only be compressed slowly by applying constant pressure.To avoid damage, do not apply more force than necessary when compressing the toothed belt tensioner. — Applying constant and moderate force, use hexagon key to press toothed belt tensioner anti-clockwise in direction of (arrow) until piston of tensioner can be locked with locking plate T10008.
32. Loosen nut (1) for tensioning roller.
33. Tension toothed belt .
34. Use a hexagon key to turn toothed belt tensioning roller in direction of (arrow) until dimension (a) is attained.
35. Turn back toothed belt tensioning roller, but do not slacken completely.
36. Turn toothed belt tensioning roller in direction of (arrow) using a hexagon key until markings (1 and 2) are aligned.
37. Tighten nut (3) for tensioning roller. [Note: Marking (1) (right edge of projection) must coincide with marking (2).]
38. ⚠ The engine must only be turned at the crankshaft, in the direction of normal engine rotation (clockwise). — Turn crankshaft two rotations via toothed belt sprocket bolt until it is positioned at TDC again.
39. Check toothed belt tension: marking (1) must be between markings (arrows); correct tension if necessary.
40. Install poly V-belt tensioner (arrows).
41. Install poly V-belt .
42. Install top section of toothed belt cover (make sure it engages securely on centre section of toothed belt cover).
43. Secure top section of toothed belt cover (arrows).
44. Install lock carrier with attachments General body repairs, exterior50.
45. Install front bumper cover General body repairs, exterior63.

Other AUDI procedures

• Removing and installing coolant pipe (bottom) – Audi
• Checking fuel gauge senderG – Audi Q7
• Removing and installing activated charcoal filter – Audi A3
• Removing and installing thermostat housing with map-controlled engine cooling thermostat F265
• Removing and installing fuel gauge sender – VW Golf V / Jetta
• Removing and installing toothed belt – Audi · 56 torque figures
• Removing engine – Audi A8 D3 · 41 torque figures
• Removing camshaft timing chain from camshafts – Audi A6/A7 C7 · 38 torque figures
• Installing engine – Audi A8 D4 · 36 torque figures
• Removing and installing camshaft timing chain · 29 torque figures