M273 in W212 — MERCEDES-BENZ

🧭 Before you start

Remove the ancillaries, covers and centrifuge, set the engine to 55° BTDC and check the camshafts. Lock the backlash adjuster, loosen the gearwheels with a counterhold, separate the chain and fit the new one with an assembly link. Remove and refit both camshafts per bank with adjusters and pulse wheels, fit the tensioner, unlock it and tension it by turning 90°. Recheck the markings, reseal the covers and refit the rest in reverse.

Fits: platform codes 500, 4MATIC, |, -T

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

Don't miss

• Always renew the timing chain and use a new assembly link.
• The 55° BTDC position shows as 305° on the crankshaft pulley.
• The oil centrifuge unscrews with a left-hand thread.
• Apply sealant bead 1.0 ± 0.5 mm and allow 10 minutes before continuing.
• Fit the cylinder head front covers without damaging the fitted sleeves.

Written for this job from the workshop steps below · TorqFix editorial.

🔧 Engine codes this applies to

📐 38 workshop diagrams for 273.970

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

📋 Procedure

Preparation and removal

1. Always renew the timing chain
2. Timing chain assembly links:
3. Ignition coil
4. Remove the cloth
5. Disconnect the battery earth cable

6. Extractor:
7. Timing chain separating tool:
8. Remove the air filter housing
9. Front cover
10. Fit the timing chain holding tool
11. Use the special tool alignment pins
12. Until the special tool alignment pins can be removed
13. Remove the spark plugs
14. Remove the air filter inlet
15. Fit the special tools
16. Remove the engine lower covers
17. Disconnect the radiator fan wiring
18. Tighten the special tool
19. Remove the ancillary drive belt
20. Remove the alternator
21. Note: The crankshaft pulley mark will be 305°
22. Turn the crankshaft to 55° BTDC for cylinder 1
23. The pulse wheel markings must be centered in the sensor location holes
24. Check the position of the camshafts
25. Remove the chain tensioner
26. Turn the crankshaft 1 rotation
27. Remove the air shut-off valve
28. Remove the bolts
29. Move the air pump switch-over valve aside
30. Disconnect the camshaft position sensors
31. Remove the cylinder head front cover
32. Use a pry bar at the points shown
33. Disconnect the hose
34. Remove the centrifuge cover
35. Remove the centrifuge
36. Note: Left-hand thread
37. From the rear of the cylinder head
38. Lock the camshaft backlash adjuster
39. Punch diameter:
40. To both camshafts
41. Loosen the camshaft gearwheel (exhaust)
42. When loosening, always use the tool to counterhold
43. From the rear of the cylinder head
44. Remove the camshaft pulse wheel
45. Check the dowel pin(s) for damage
46. Remove the exhaust camshaft timing adjuster
47. Remove the sealing cap
48. Loosen the camshaft gearwheel (inlet)
49. When loosening, always use the tool to counterhold
50. Disconnect the right-hand connector from the control unit (viewed from the rear of the engine)
51. Disconnect the control unit with the wiring and place it on the engine
52. Remove the control unit bracket
53. Note: Always renew the component
54. Remove the cable guide
55. Remove the cylinder head cover
56. Use a special tool(s) to remove the chain tensioner rail bolt
57. Pull it upwards
58. From the rear of the cylinder head
59. Remove the camshaft pulse wheel
60. Check the dowel pins for damage
61. Remove the timing chain from the camshaft gearwheel
62. Remove the inlet camshaft timing adjuster
63. From the rear of the cylinder head
64. Remove the punch used to lock the camshaft backlash adjuster

Installation and checks

65. Use a timing chain assembly link
66. Note: Avoid bending, torsion or traction
67. Remove the special tool
68. Turn the rivet tool until resistance is felt
69. Right cylinder head:
70. Refit the camshaft bearing caps
71. Refit the inlet camshaft timing adjuster
72. Note: When removing/fitting the covers, do not damage the fitted sleeves
73. Align the coloured chain link with the mark on the crankshaft gearwheel
74. Align the locating pins shown
75. Exhaust camshaft:
76. Fit the exhaust camshaft
77. Note: Finger-tight only
78. Refit the exhaust camshaft timing adjuster
79. Refit the cylinder head cover
80. Inlet camshaft:
81. Remove the inlet camshaft
82. Note: In an anti-clockwise direction
83. While counterholding the exhaust camshaft
84. Apply a torque of 70 Nm to the crankshaft centre bolt
85. Fit the tools as shown
86. Separate the timing chain
87. Remove the counterhold tool
88. Note: This will tension the new hydraulic tensioner
89. Turn the crankshaft 90° in the direction of rotation
90. Note: Left-hand thread
91. Stage 1:
92. Stage 2:
93. Refit the centrifuge
94. Stage 1:
95. Stage 2:
96. Refit the centrifuge cover
97. Refit the oil breather pipe
98. Note: When removing/fitting the covers, do not damage the fitted sleeves
99. Refit the cylinder head front cover
100. Note: The bead thickness must be 1.0 ± 0.5 mm
101. To both sides
102. Apply sealant as indicated
103. Wait for 10 minutes
104. Note: The crankshaft pulley mark will be 305°
105. Turn the crankshaft to 55° BTDC for cylinder 1
106. The pulse wheel markings must be centered in the sensor location holes
107. Check the position of the camshafts
108. Correct if necessary
109. Refit all other parts in the reverse order of removal

Other MERCEDES-BENZ procedures

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