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Mercedes-Benz Vito: OM646 Timing Chain Tensioner Premature Wear

OM646 Timing Chain Tensioner Premature Wear is a common engine fault on the Mercedes-Benz Vito on the 2003–2010 cars, and we rate it major. Putting it right costs $1,500 to $3,800 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 16 documented faults on the Mercedes-Benz Vito.

Vehicle
Mercedes-Benz Vito
Engine
2.1L
Years
2003–2010
Fuel
diesel
System
Engine

This page covers the Mercedes-Benz Vito as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All Mercedes-Benz Vito faults16 documented faults on this model

What you are looking at

The front of a dual overhead camshaft engine with the timing cover removed, exposing the timing chain and sprockets.Example of the part — not this vehicle

The front of a twin-cam engine with the timing cover off — chain, sprockets and guides.

Logansenf · CC BY-SA 4.0 · Wikimedia Commons

What goes wrong

The OM646 2.2CDI engine fitted to early W639 Vito models is subject to documented premature timing chain tensioner wear, allowing the chain to develop slack and stretch. Mercedes-Benz formally addressed this via Service Bulletin SWE-09-12, prescribing an upgraded replacement tensioner (OEM part A6460502201) and new guide rails across all affected W639 Vito models. If the loose chain is not detected early, it can jump teeth on the camshaft sprockets, resulting in valve-to-piston contact and catastrophic engine damage. The issue is most prevalent in pre-2010 production.

What you would notice

  • Cold-start rattling or slapping from front of engine that may diminish when warm
  • Check engine light with camshaft-to-crankshaft correlation fault codes
  • Rough idle on startup
  • Occasional misfires immediately after cold start

How to check it

Where to look. Front of engine behind timing chain cover

Start the engine from fully cold and listen carefully for chain rattle or slapping from the front of the engine. Allow engine to warm and recheck — persistent rattle is more serious than a noise that fully clears. Confirm in service records whether the SWE-09-12 tensioner upgrade has been completed. If a workshop inspection is possible: Connect a diagnostic scanner and check for P0016 or P0017 cam-crank correlation fault codes.

Parts involved: Timing chain.

What it costs to put right

$1,500 to $3,800 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

  • “Has the timing chain tensioner been upgraded per Mercedes Service Bulletin SWE-09-12?”
  • “Does the engine rattle or tick on cold start before clearing when warm?”
  • “What is the documented engine service history?”

Now check the Mercedes-Benz Vito you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.

Mercedes-Benz Vito buyer questions

Is om646 timing chain tensioner premature wear serious on a Mercedes-Benz Vito?

We rate it major and common on the Mercedes-Benz Vito. The OM646 2.2CDI engine fitted to early W639 Vito models is subject to documented premature timing chain tensioner wear, allowing the chain to develop slack and stretch. Mercedes-Benz formally addressed this via Service Bulletin SWE-09-12, prescribing an upgraded replacement tensioner (OEM part A6460502201) and new guide rails across all affected W639 Vito models. If the loose chain is not detected early, it can jump teeth on the camshaft sprockets, resulting in valve-to-piston contact and catastrophic engine damage. The issue is most prevalent in pre-2010 production.

How much does it cost to fix on a Mercedes-Benz Vito?

$1,500 to $3,800 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which Mercedes-Benz Vito years are affected?

Our research records this fault on the 2003–2010 Mercedes-Benz Vito. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.

How do I check for it before I buy?

Start the engine from fully cold and listen carefully for chain rattle or slapping from the front of the engine. Allow engine to warm and recheck — persistent rattle is more serious than a noise that fully clears. Confirm in service records whether the SWE-09-12 tensioner upgrade has been completed. If a workshop inspection is possible: Connect a diagnostic scanner and check for P0016 or P0017 cam-crank correlation fault codes. Look here: Front of engine behind timing chain cover