TorqFix

OM651 in W639 — MERCEDES-BENZ

OM651 in W639 on Mercedes-Benz: 110 steps, engines 651.940, 651.942. What to remove, in what order, and what to check after.

Timing chain renewal on the OM651 four-cylinder diesel (651.940, 651.942) in the W639 Viano and Vito, including the 4MATIC versions. As on most Mercedes chain jobs of this period, the old chain stays in place and the new one is linked to it and drawn round the gearwheels, then closed with the chain assembly tool. Before that the injection lines and injectors come out, the engine wiring loom, fuse box and air inlet duct are moved off, and the cylinder head cover and tensioner piston are removed. The crankshaft then goes to TDC for cylinder 1 and the marks are checked; if they do not line up, the camshafts have to come out and be refitted in the right position.

110 steps 2 engine codes

🧭 Before you start

Remove the engine upper cover, injectors, injection lines, wiring loom, fuse box and cylinder head cover, then take out the chain tensioner piston. Separate the old chain, join the new chain to it and pull it round, then close the joining link with the assembly tool. Check the timing marks at TDC, correcting camshaft position if needed, rebuild in reverse and finish with a fault code check, engine run and leak check.

Fits: platform codes VIANO, CDI, 2.0, |, 4MATIC, 2.2, VITO, 110, 113, 116

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

Don't miss

  • Do not drop any timing chain pins into the crankcase; cover the chain housing with a clean cloth.
  • Store the injectors in order and plug the open holes while they are out.
  • If the marks are misaligned at TDC for cylinder 1, remove and refit the camshafts rather than forcing it.
  • The injector clamps are tightened in stages; follow the stage order when refitting.
  • As general practice, renew the injector sealing washers whenever the injectors are pulled.

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

🔧 Engine codes this applies to

651.940651.942

📐 22 workshop diagrams for 651.940

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

OM651 in W639 — 651.940 · diagram 1
OM651 in W639 — 651.940 · diagram 2
OM651 in W639 — 651.940 · diagram 3
OM651 in W639 — 651.940 · diagram 4
OM651 in W639 — 651.940 · diagram 5
OM651 in W639 — 651.940 · diagram 6
OM651 in W639 — 651.940 · diagram 7
OM651 in W639 — 651.940 · diagram 8
+ 14 more diagrams
🔒 22 workshop diagrams for this job Ask about your Mercedes-Benz 651.940 — free or sign up free to see the drawings

📋 Procedure

Preparation and removal

  1. Injector
  2. Remove the engine upper cover
  3. Turn the engine until the chain connecting link shows
  4. Disconnect the chain
  5. Timing chain separating tools:
651.940? Steps differ between engine variants — check this job against your exact car before you commit to it. Check my car — free →
  1. Timing chain assembly tools:
  2. Timing chain separating tools:
  3. Timing chain assembly tool:
  4. Timing chain separating tools:
  5. Disconnect the fuel lines from the injectors
  6. Remove the injection lines
  7. Disconnect the camshaft position sensor electrical connector
  8. Remove the fuel return hoses from the injectors
  9. Disconnect the fuel injector wiring
  10. Remove the fuel injector clamps
  11. Remove the injectors
  12. Plug the holes
  13. Store in order
  14. Disconnect the engine control unit
  15. Disconnect the connectors
  16. Remove the fuse box
  17. Remove the engine wiring loom
  18. Remove the air inlet duct
  19. Disconnect the oxygen sensor
  20. Remove the engine wiring loom
  21. Disconnect the exhaust gas pressure sensor
  22. Disconnect the connectors
  23. Disconnect the positive crankcase ventilation hose
  24. Disconnect the fuel return line
  25. Remove the cylinder head cover
  26. Remove the bracket
  27. Automatic transmission:
  28. Remove the oil filler tube
  29. All vehicles:
  30. Remove the heat shield(s)
  31. Remove the chain tensioner piston
  32. Separate the timing chain
  33. Note: Cover the timing chain housing with a clean cloth

Installation and checks

  1. Connect the ends of the new chain
  2. Use the special tools to remove the timing chain pins
  3. Note: Do not drop any timing chain pins into the crankcase
  4. Remove the special tools
  5. Pull the removed timing chain pins out of the chain separating tool
  6. Tighten the special tool
  7. Refit the chain tensioner piston
  8. Refit the heat shield(s)
  9. Automatic transmission:
  10. Refit the oil filler tube
  11. All vehicles:
  12. Refit the bracket
  13. Turn the crankshaft to TDC for cylinder 1
  14. Check the position
  15. If the marks are misaligned
  16. Remove the camshafts
  17. Fit the camshafts
  18. Refit the cylinder head cover
  19. Reconnect the fuel return line
  20. Reconnect the positive crankcase ventilation hose
  21. Reconnect the connectors
  22. Reconnect the exhaust gas pressure sensor
  23. Refit the engine wiring loom
  24. Reconnect the oxygen sensor
  25. Refit the air inlet duct
  26. Refit the engine wiring loom
  27. Refit the fuse box to the mounting bracket
  28. Reconnect the connectors
  29. Reconnect the engine control unit
  30. Refit the injectors
  31. Refit the fuel injector clamps
  32. Stage 1:
  33. Stage 2:
  34. Reconnect the fuel injector wiring
  35. Union nut:
  36. Stage 1:
  37. Stage 2:
  38. Reconnect the fuel lines to the injectors
  39. Stage 1:
  40. Stage 2:
  41. Reconnect the battery earth cable
  42. Check for any fault codes
  43. Run the engine
  44. Check for leaks
  45. Refit the engine upper cover
Workshop diagrams

Ask TorqFix about your Mercedes-Benz 651.940 — it answers with the exact sequence for that engine and the workshop drawing for each step. First question is free after a 20-second sign-up, no card.

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TorqFix was built by a mechanic — after a 2,700 km drive with five roadside repairs that no diagnostic tool could explain.

The figures on this page come from manufacturer workshop documentation and are shown as they are. The page is assembled automatically from that data — it is not written by an AI. The AI works in the chat, where it answers for your specific car. It writes nothing here.

Variants of the same model differ. Cross-check torque against the factory manual for your engine before final tightening.

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Workshop data on this page last updated 20 Sep 2026.