vinkodex.Chain tensioner: the check valve is missing from the oil supply
Typically above 60,000 km. It does not show up on every car.
expensive
severity
above 60,000 km
mileage
3
sources
3 sources next to the write-up.
The fault
How you spot it
The check valve is missing from the oil supply of the timing chain tensioner. With the engine stopped the oil drains out of the passage, so at start-up the tensioner does not get pressure straight away, and over time that wears it out. On early production examples it appears from as little as 60 000 kilometres.
The tensioner does not hold the chain, the chain goes slack and the valve timing shifts. The symptom is a metallic rattle audible at a cold start which quietens after a few seconds. If the chain jumps, the valves and the pistons meet.
The same noise is also produced by a failure of the camshaft adjuster, and there the fault code gives the direction: P001685, P001785, P001177 and P001885 belong to it.
The repair is not an engine strip. The tensioner can be reached after the charge air cooler and the front cover have been removed, and from there two screws hold it. The prevention is fitting the check valve into the oil supply.
Which model
Who it affects
The card opens the generation, the engine or the transmission.
Engines and transmissions
Engine
M278DE46AL
vinkodex.Checklist
Chain tensioner: the check valve is missing from the oil supply
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Checklist
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Sources
How we know
- 603mtech.comM278 gyakori hibai: a hianyzo visszacsapo szelep az olajellatasban, es a vezermutengely-allito kodjai603mtech.com
- automotivetechinfo.comMercedes lancfeszitok szaklap-cikke: a feszito a toltolevego-huto es az elulso fedel mogott, ket csavarralautomotivetechinfo.com
What BreaksMercedes-Benz S-Klasse W221 — All Engines, Problems & Buying Guide (2005–2013)Mercedes-Benz S-Klasse W221: 70 common defects and weaknesses. 8 engines (OM651DE22, M272, M273, OM642, …), 204–612 hp. Reviews, durability and buying advice 2005–2013.
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.
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