Car Model Guide/ Issues/ Timing chain and sprocket wear (early OM651)

Timing chain and sprocket wear (early OM651)

Attaches to OM651 at engine level · Engine · carried by 8 variants across 4 chassis

Overview

Timing chain and sprocket wear (early OM651) is a common fault recorded against OM651 at engine level, typically from 90–180k km. It shows up as a rattle or whirr from the front of the engine for two or three seconds on cold start; at worst the chain jumps teeth and bends valves. Where it's documented, the repair runs €900–€2,500 (chain, sprockets and tensioner at a specialist, costs dated 2026-07), and it can be partly checked before you buy. 8 variants across 4 chassis in this database inherit it.

€900 – €2,500

chain, sprockets and tensioner at a specialist · costs dated 2026-07

Likelihoodcommon

Typical onset90–180k km

Detectablepartially

Walk awayno

Evidencedocumented

What happens

Symptom. A rattle or whirr from the front of the engine for two or three seconds on cold start; at worst the chain jumps teeth and bends valves.

Cause. The early oil-fed tensioner and camshaft sprocket design on pre-2012 OM651 engines wears; Mercedes revised the sprockets, tensioner and cover for later cars. Extended oil intervals and low oil level make it worse.

Later parts. Revised sprockets, tensioner and cover from around 2012

How to check it

Cold start

Listen at a genuinely cold start on any pre-2012 car for a front-of-engine rattle, and favour a car with the revised sprockets or documented chain work.

You get one. If the engine is warm when you arrive, come back another day.

EnginecommonPartly detectableevidence: documented90–180k km

Every variant that carries this

Variant	Chassis	Body	Years	Risk	Good buy	Cost as % of good buy
C 220 CDI OM651	W204	sedan	2009–2014	R3	€5,700	30%
C 220 CDI OM651	S204	wagon	2009–2014	R3	€6,000	28%
E 220 CDI OM651	W212	sedan	2009–2016	R3	€6,300	27%
E 220 CDI OM651	S212	wagon	2009–2016	R3	€6,650	26%
E 200 CDI OM651	W212	sedan	2010–2016	R3	€5,500	31%
E 200 CDI OM651	S212	wagon	2010–2016	R3	€5,800	29%
E 250 CDI OM651	W212	sedan	2009–2016	R3	€7,300	23%
E 250 CDI OM651	S212	wagon	2009–2016	R3	€7,700	22%

The last column is the point. The same repair is an inconvenience on one variant and a reason to scrap the car on another. A failure costing a quarter of the vehicle's value changes the purchase decision regardless of how rare it is.