P0016 on Mercedes-Benz

The turbo petrol M270 (and naturally-aspirated M270/M274 in B180/B200/B250) uses a two-stage timing chain whose plastic guide rails and hydraulic tensioner degrade prematurely. Owners report a loud metallic rattle for roughly 1-15 seconds on cold start that fades as oil pressure builds. Short-trip urban use accelerates the problem because the cold-start period (low oil pressure) makes up a large share of running time. Stretch typically appears from ~80,000 km (50,000 mi), with some city cars rattling from ~70,000 km. Left unaddressed, chain stretch alters valve timing, throws fault codes, and risks contact/wear on cam bearings and phasers.

On certain 2015-2016 CLA-Class cars with the 2.0L turbo M270/M274 engine, one or both camshafts were manufactured with a weld outside specification. The defective weld can fail and cause the camshaft to break, damaging the engine, causing sudden loss of power and an engine stall while driving. This is the subject of NHTSA safety recall 15V662 (covering CLA, GLA and SLK). Separately, owners more broadly report camshaft-adjuster rattle/wear on these engines that should not be confused with the recalled welded-camshaft defect.

The M272 V6 and M273 V8 engines in early CLS models suffer from a well-documented balance shaft gear failure where the idler gear sprocket wears prematurely due to a manufacturing defect. The worn gear produces a rattling noise on startup and can eventually cause engine timing issues and catastrophic damage if the gear teeth strip completely.

The M272 3.5L V6 has a defective balance shaft gear that wears prematurely due to a soft sprocket material used in early production. When the gear teeth strip, the balance shaft stops functioning, causing severe engine vibration and potential timing chain skip.

The 5.5L M157 biturbo V8 used in the W463 AMG G 63 before the 2019 redesign is documented for cylinder wall scoring/scuffing at higher mileage plus weaknesses in timing-chain components and camshaft (VVT) adjusters. The camshaft adjuster magnets/solenoids meter oil to the VVT and chain; restricted flow accelerates chain and gear wear. Oil intrusion into the camshaft position sensor wiring can also mimic internal engine faults. Symptoms range from multi-cylinder misfires to rattle and, in worst cases, metal in the oil from bore scoring.

The GLA's M270/M274 turbo four-cylinder petrol engines are widely documented to suffer timing chain elongation and tensioner/guide wear, usually presenting between roughly 40,000-80,000 mi. A loose chain produces a distinctive rattle for the first few seconds after a cold start until oil pressure loads the tensioner. A related defect is the camshaft tone/reluctor ring slipping, throwing timing-correlation faults. Left unaddressed, a stretched chain can jump time and cause valve-to-piston contact and major engine damage.

On the M274/M264 2.0L turbo engines used in the GLC, the intake camshaft adjuster relies on an internal locking pin that wears over time. Without oil pressure at cold start, the adjuster fails to lock in its default position, producing a distinct metallic rattle for 2-4 seconds on a cold start. Oil leaking around the camshaft adjuster solenoid can also seep into the wiring harness and trigger timing faults. Left unrepaired it risks valve-timing errors and further engine wear.

The base GLE 350's M264 2.0L turbo four-cylinder can develop a worn/weak timing chain tensioner and chain stretch, producing a rattle (often on cold start or under load) from the front of the engine. If ignored, chain stretch can throw camshaft/crankshaft correlation codes and, in the worst case, cause valve-to-piston contact. Metal shavings in the oil or a check-engine light for timing correlation are red flags.

The M278 4.7L biturbo V8 used in the GLE 550 4MATIC (W166/C292) has a complex timing drive with one primary chain and two secondary chains, each with its own tensioner. On early engines the secondary chain tensioners lose oil pressure during shutdown because they lack anti-drainback check valves, so on cold start the chains and camshaft adjusters run momentarily dry and rattle loudly for the first 2-5 seconds until oil pressure builds. Left unaddressed, chain slack, worn guide rails, and worn camshaft adjusters can advance to camshaft-correlation faults and, in the worst case, timing jump. This is distinct from the M276 V6 camshaft-adjuster rattle: it is the V8 M278's multi-chain oil-starvation design, and Mercedes issued a service fix (TSB LI05.10-P-056435) adding oil check valves plus revised secondary tensioners for engines up to a specific engine-number cutoff (278 9xx).

The M272 V6 engine in ML350 models is affected by the same balance shaft sprocket wear issue found across all Mercedes M272-equipped vehicles. The idler gear wears prematurely, producing a progressively worsening rattle on startup and eventually causing timing chain faults. This is a well-documented manufacturing defect that Mercedes addressed with updated parts.

The M276 3.5L V6 used in the W166 ML350 develops a brief but distinct rattle on cold start-up. After the car sits, oil drains from the front timing covers to the sump, leaving the secondary chain tensioners momentarily without pressure on startup. The result is chain/adjuster rattle for 1-3 seconds at first fire. Underlying contributors can include failed chain tensioners, worn camshaft adjusters, a stretched timing chain and/or worn guide rails. If ignored, severe cases risk chain/guide damage. Mercedes addressed this in TSB LI05.10-P-056435 by adding oil check valves to the tensioner oil-supply passages.

The R231 SL with M276 V6 or M278 V8 engines develops a distinctive rattling noise from the timing chain area on cold starts. The cam adjuster magnets (variators) lose oil pressure overnight, allowing the chains to slap against the guides until oil pressure builds. This noise worsens over time and can eventually lead to stretched chains and timing issues.

The SLC 43 AMG's M276 DE30LA 3.0L biturbo V6 commonly develops a loud rattle for a few seconds at cold start as the camshaft adjusters (variable valve timing solenoid units) and their solenoid magnets wear, losing the ability to hold oil pressure/timing on shutdown. The engine has four adjusters; when worn they produce the characteristic startup rattle and can set camshaft-correlation/position fault codes, with risk of extended crank, rough running, and timing deviation if left unaddressed. This is a well-documented M276 trait, typically appearing past ~60k-100k miles.

Certain M272 V6 engines used in the SLK280 and SLK350 can suffer premature wear of the balance shaft sprocket and timing components. As the sprocket teeth wear, cam/crank correlation drifts, causing check-engine lights, rough running, poor performance, and in severe cases internal engine timing damage.

The M271 supercharged four-cylinder engine in early SLK models is prone to timing chain stretch and tensioner failure. The single-row chain stretches over time, and the hydraulic tensioner fails to take up the slack. This causes a rattling noise on startup and can lead to jumped timing and catastrophic engine damage if the chain skips teeth.

The M272 V6 engine in SLK280, SLK300, and SLK350 models suffers from the well-documented balance shaft sprocket wear issue common across all Mercedes M272-equipped vehicles. The idler gear sprocket wears prematurely due to a softer-than-specification material, producing a progressively worsening rattle and eventual timing faults.

The M271 four-cylinder's camshaft adjuster magnets (variable valve timing solenoids) commonly fail or become oil-fouled on R171 SLK200 Kompressor and R172 SLK250 models. A well-documented M271 defect is engine oil wicking up the solenoid connector into the wiring harness toward the ECU and O2 sensor. This is distinct from timing-chain/gear wear: the solenoid itself sticks or shorts, upsetting cam timing and triggering camshaft-position/correlation codes.

Many V-Class W447 models use the OM651 2.1L simplex (single-row) timing chain diesel. The plastic chain guides and the hydraulic tensioner degrade with heat, age and dirty/low oil faster than the chain itself, letting the chain go slack and stretch. Because the chain sits at the rear of the engine (against the bulkhead), the tell-tale cold-start rattle is often misattributed. Left unaddressed the chain can jump timing or snap, causing catastrophic engine damage. The later OM654 switched to a duplex chain, a tacit admission the OM651 simplex was a weak point.