{"canonVersion":{"checklist":1,"defects":2},"defectsRelease":{"format":3,"release":"2026.10.1","dossiers":15},"attribution":{"source":"Elgarde","url":"https://elgarde.com","license":"CC-BY-4.0","repository":"https://github.com/ElgardeCom/elgarde"},"disclaimer":"Elgarde is a self-service checklist, not a certified, mechanical or legal inspection and not professional advice. Defect entries are known weak points to check on a model — never a claim about any individual car.","defectsDisclaimer":"Each entry describes a known weak point of a model, engine or gearbox, based on published sources. It is not a statement about any individual car and not a diagnosis. An entry does not mean that a given car has the defect; the absence of an entry does not mean that a car is sound. Prevalence figures are estimates for the stated population and method, with their biases, and cannot be applied to a single car. The data is provided as is, without warranty (CC-BY-4.0, section 5); it is not a certified, mechanical or legal inspection. Naming a manufacturer or its product is not an assessment of that manufacturer; source links show where each fact comes from. To report an error, open an issue at github.com/ElgardeCom/elgarde or write to support@elgarde.com. We correct mistakes.","lang":"en","defect":{"id":"m271.timingchain","aliases":["m271.balanceshaft"],"revision":1,"updatedAt":"2026-10-13","title":"Mercedes M271 1.8 petrol: timing chain, tensioner and camshaft adjuster wear","summary":"Two independent German sources describe timing chain elongation on the M271 four-cylinder petrol engine (built 2002 to 2015), with a cold-start rattle, a worn tensioner and worn camshaft adjusters, and in the worst case a chain that jumps and damages the engine. One says older cars without the EVO optimisation are more affected; the other says the chain remained an issue on the EVO as well. The earlier checklist item named the balance shaft; none of the sources used here mentions it.","checklistPrompt":"M271 petrol (C/E-Class, SLK): timing chain — check for cold-start rattle and chain/tensioner replacement history","component":"engine.timing.chain","mechanism":"The M271 uses a single-row (simplex) timing chain. Gebrauchtwagenberater.de gives a defective chain tensioner as the usual cause of early elongation, with wear accelerated by late or missed oil changes, and says the camshaft adjuster sprockets can wear so that the chain jumps; mbpassion.de names wear of the chain and tensioner, says a worn tensioner can in the worst case let the chain jump, and that the camshaft adjusters wear with a worn chain, which raises the risk of engine damage. According to Gebrauchtwagenberater.de the EVO versions from 2009 changed to a toothed chain; mbpassion.de describes the earlier cars as more affected, while Gebrauchtwagenberater.de says the chain stayed an issue on the EVO. No Mercedes document on these changes was found.","applicability":{"models":[{"id":"mercedes.cclass","label":"Mercedes-Benz C-Class"},{"id":"mercedes.eclass","label":"Mercedes-Benz E-Class"},{"id":"mercedes.slk","label":"Mercedes-Benz SLK"}],"when":{"all":[{"engine":{"ids":["mercedes.m271"]}},{"productionDate":{"from":"2002-01","to":"2015-12"}}]},"markets":["EU"],"hint":"Only Mercedes four-cylinder petrol engines of the M271 family (1,796 cc), built 2002 to 2015 according to the sources: the supercharged versions and the later turbocharged EVO versions. The sources say cars without the EVO changes are more affected. Mercedes V6 and V8 engines (M272, M273) are not part of this entry.","notes":"The legacy checklist item for this engine named a balance shaft; this entry covers the timing chain, which is what the sources describe. Engine sub-codes and the exact date of the EVO change are not given in the sources used. One source says the M271 was also used in other, lower-volume Mercedes models without naming them, so the model list may be incomplete. The only sources are two independent specialist articles; no manufacturer document, recall, regulator record or failure rate was found."},"engines":[{"id":"mercedes.m271","family":"M271","codes":["M271"],"fuel":"petrol","displacementCc":1796,"powerKw":[],"label":"Mercedes M271 1.8 petrol (supercharged and EVO)"}],"gearboxes":[],"severity":"major","safety":false,"critical":false,"evidenceGrade":"well_documented","symptoms":[{"id":"s1","text":"Rattling from the front of the engine at cold start and under load changes","stage":"early"},{"id":"s2","text":"Chain jumping a tooth after a worn tensioner or adjusters, with possible engine damage","stage":"late"}],"inspection":[{"id":"i1","method":"document","text":"Confirm the engine is an M271 and the build date; ask whether the timing chain, tensioner, guides and camshaft adjusters were ever replaced, and ask for the oil-change history.","redFlag":"No chain work on record and late or missed oil changes.","tools":[]},{"id":"i2","method":"listen","text":"Start the engine fully cold and listen at the front of the engine for a metallic rattle, then listen again under changing load.","redFlag":"Rattle: have a specialist measure the chain elongation before buying.","tools":[]},{"id":"i3","method":"obd","text":"Read the fault memory for camshaft timing correlation faults; Gebrauchtwagenberater.de says the manufacturer offers a check of chain elongation with a measuring chain tensioner.","redFlag":"Camshaft timing faults stored.","tools":[]}],"repair":{"remedy":"Replacement of the timing chain together with the tensioner, guides and camshaft adjusters, as the sources advise replacing them together. No cost figure is given in the sources used here.","cost":null,"worstCase":null,"manufacturerProgramme":null},"evidence":["ev_bmmb_e15","ev_bmmb_e16"],"prevalence":["pv_m271_none"],"disclaimer":"Each entry describes a known weak point of a model, engine or gearbox, based on published sources. It is not a statement about any individual car and not a diagnosis. An entry does not mean that a given car has the defect; the absence of an entry does not mean that a car is sound. Prevalence figures are estimates for the stated population and method, with their biases, and cannot be applied to a single car. The data is provided as is, without warranty (CC-BY-4.0, section 5); it is not a certified, mechanical or legal inspection. Naming a manufacturer or its product is not an assessment of that manufacturer; source links show where each fact comes from. To report an error, open an issue at github.com/ElgardeCom/elgarde or write to support@elgarde.com. We correct mistakes."},"evidence":[{"id":"ev_bmmb_e15","type":"specialist_press","tier":2,"defects":["m271.timingchain"],"supports":["existence","mechanism","symptom","applicability","inspection"],"scope":{"all":[{"engine":{"ids":["mercedes.m271"]}},{"productionDate":{"from":"2002-01","to":"2015-12"}}]},"source":{"publisher":"Gebrauchtwagenberater.de","title":"Mercedes M271 Probleme und Schwachstellen","url":"https://gebrauchtwagenberater.de/m271-probleme/","identifier":null,"publishedDate":"2026-08-17","retrievedAt":"2026-10-13","language":"de","archive":{"url":"https://web.archive.org/web/20260315115038/https://gebrauchtwagenberater.de/m271-probleme/","capturedAt":"2026-03-15","sha256":null},"license":"proprietary","reuse":"cite","status":"archived"},"quote":null,"translation":null,"note":"German used-car guide: M271 (1,796 cc four-cylinder, built 2002 to 2015; EVO versions from 2009). The chain was changed from duplex to simplex; the simplex chain is known for early elongation that can lead to major engine damage; the guide gives a defective chain tensioner as the cause, with wear accelerated by late or missed oil changes. Symptoms: rattling at cold start and under load changes; camshaft adjuster sprockets can wear and let the chain jump, so the guide advises replacing them with the chain. On the EVO (toothed chain instead of roller chain) it says the chain remained an issue. No failure percentage, balance-shaft or manufacturer-programme information is given.","confidence":"medium","reviewedAt":"2026-10-13","reviewStatus":"source_verified"},{"id":"ev_bmmb_e16","type":"specialist_press","tier":2,"defects":["m271.timingchain"],"supports":["existence","mechanism","symptom","applicability"],"scope":{"all":[{"engine":{"ids":["mercedes.m271"]}},{"productionDate":{"from":"2002-01","to":"2015-12"}}]},"source":{"publisher":"mbpassion.de","title":"Mercedes M271 Motor: Probleme, Schwachstellen und Tipps für Gebrauchtwagenkäufer","url":"https://mbpassion.de/2026/02/mercedes-m271-motor-probleme-schwachstellen-und-tipps-fuer-gebrauchtwagenkaeufer/","identifier":null,"publishedDate":"2026-02-08","retrievedAt":"2026-10-13","language":"de","archive":{"url":"https://web.archive.org/web/20260306053534/https://mbpassion.de/2026/02/mercedes-m271-motor-probleme-schwachstellen-und-tipps-fuer-gebrauchtwagenkaeufer/","capturedAt":"2026-03-06","sha256":null},"license":"proprietary","reuse":"cite","status":"archived"},"quote":null,"translation":null,"note":"German Mercedes enthusiast magazine: M271 built 2002 to 2015 in the C-Class, E-Class and SLK. Rattling at cold start; many engines develop chain elongation before 100,000 km; the cause is wear of the chain and tensioner, and older models without the EVO optimisation, which have the simple simplex chain, are said to be more affected; a worn tensioner can in the worst case let the chain jump. Camshaft adjusters wear with a worn chain, which raises the risk of engine damage. The article does not mention a balance shaft or a manufacturer programme.","confidence":"medium","reviewedAt":"2026-10-13","reviewStatus":"source_verified"}],"prevalence":[{"id":"pv_m271_none","kind":"none","value":null,"unit":null,"numerator":null,"denominator":null,"ci":null,"population":null,"outcome":null,"baseline":null,"method":null,"evidence":["ev_bmmb_e15","ev_bmmb_e16"],"confidence":null,"caveats":[],"noReliableFigure":true,"reason":"No verified share of M271 engines with timing chain wear has been published; the two articles used give no failure percentage (mbpassion.de says many engines show elongation before 100,000 km, without a number)."}],"attributions":[]}