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Engine code

OM656D29SCR engine faults.

The listing only gives the engine code.

diesel

fuel

2925 cc

displacement

243 kW (330 HP)

power

2 fault write-ups. Both are important.

Before you buy

Known faults

2 important faults

critical1

OM654 / OM656: vacuum controlled coolant pump leak, fire risk

critical

On the OM654 and OM656 diesels the maker started a recall over the vacuum controlled coolant pump (maker action code: 2090008). The fault: a leak can develop between the coolant and the vacuum circuit; if coolant reaches the electric switching valves, an electrochemical reaction can raise the temperature of the part, and a fire risk cannot be ruled out.

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The fix: replacing the electric switching valve and a software update. The campaign started at the end of 2021; the affected group is the C-Class, E-Class and other OM654/OM656 models.

A recall on the model does not mean it was carried out on this car. Only the franchised dealer can tell you, by VIN.

What to check

  • Ask the franchised dealer by VIN: is action 2090008 OPEN or CLOSED
  • Check the coolant level and look around the vacuum system for leaks
  • Ask for the service sheet: a switching valve replacement plus a software update is part of the campaign
1 more steps in the write-up

expensive1

OM654 / OM656 diesel: roller finger follower wear and DPF driven oil dilution

expensive

The modern OM654 four cylinder diesel (and the modular OM656 six cylinder) carries two weaknesses on the used market that reinforce each other.

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1) Roller finger followers (Rollenschlepphebel). According to the German technical press, on some cars the followers wear early at around 100,000 to 120,000 km. On 10 July 2018 the maker introduced a strengthened follower from engine number 80278367 (new part number A6540505701 in place of the old A6540501100). On early built cars the risk is higher. A faulty follower develops so much heat that the removed metal shows blue discolouration (Anlaufspur).

2) Oil dilution. The post injection needed to regenerate the particulate filter puts diesel fuel into the engine oil. With short urban use the engine does not get warm enough, the fuel does not evaporate, the oil thins out, and the follower and valvetrain are exactly what suffers most from poor lubrication.

The timing chain sits on the gearbox side: if it stretches, the replacement is labour intensive. There are few complaints of a broken chain, but on the early series about 5,000 cars were recalled for a weak chain, and the Tritan 15 coating was changed to Tritan 18.

between 80,000 and 160,000 km

What to check

  • Listen to the engine on a cold start: metallic ticking or rattling from the follower or the chain is suspect
  • Ask for the engine number: cars below 80278367 (before July 2018) are the old follower group
  • Check the service book: how often and with what oil (MB 229.52 is recommended) it was changed. Long intervals plus urban use is the worst pairing
2 more steps in the write-up

Engine code

Factory data

Factory data

Engine family
—
Fuel
diesel
Displacement
2925 cc
Power
243 kW (330 HP)
Production
—

Generations

Which models it is fitted to

3 generations.

Information, not an expert opinion

We write the descriptions, and we put the source next to them. A person reviews them before they go out. They are still information, not a technical expert opinion.

  • A fault on the list does not mean the car you are looking at has it.
  • A fault missing from the list does not mean the model is fault-free. Write-ups are made model by model. Not all of them are done.
  • You decide whether to buy. This is no substitute for an inspection. That needs a workshop and a history check.
Details in the terms