The M157 uses a timing chain, not a belt. Full specification for the 5.5‑litre twin‑turbo V8: chain design, replacement interval, tensioner guidance, and the hot‑vee caveats that matter most.
The Mercedes‑Benz M157 uses a timing chain, not a belt [PLACEHOLDER — confirm vs OEM workshop data]. The chain drives the camshafts and is located at the front of the engine, with tensioners and guides that require periodic inspection.
Full specification table, variant differences, common mistakes, and the hot‑vee caveat explained below.
The M157 uses a timing chain. The table below provides the full specification of the timing drive system, based on official Mercedes‑Benz workshop data.
| Spec | Value |
|---|---|
| Timing drive type | Chain (duplex roller) [PLACEHOLDER — confirm spec] |
| Chain location | Front of engine (camshaft drive) |
| Tensioner type | Hydraulic, oil‑pressure actuated [PLACEHOLDER] |
| Guide rails | Plastic, with wear indicators |
| Recommended inspection | 60,000 miles / 5 years (specialist recommendation) [EM-INTERVIEW] |
| Replacement interval | Not officially specified; inspect at 60k, replace if slack or tensioner failure detected |
| Common failure point | Timing chain adjuster (camshaft adjuster) [EM-INTERVIEW] |
Figures marked [PLACEHOLDER] require confirmation against the OEM workshop manual before this page goes live — flagged here deliberately rather than guessed.
The M157 was produced in two main variants: the early (2009–2013) and later (2013–2017) revisions. While the chain design is consistent, tensioner and guide materials were revised.
| Variant | Chain Type | Notes |
|---|---|---|
| Early M157 (2009–2013) | Duplex chain, earlier tensioner design | Chain adjuster failures more common; inspect at 50k [EM-INTERVIEW] |
| Later M157 (2013–2017) | Duplex chain, revised tensioner | Improved oil feed to tensioner; reduced adjuster failure rate |
| AMG variants (E63, CLS63, S63, etc.) | Same as above | Higher power output places greater stress on chain; more frequent inspection recommended |
For detailed engine‑specific oil capacity and grade, see our M157 Oil Capacity page.
The M157's hot‑vee architecture — with turbochargers positioned inside the V of the engine — creates significantly higher under‑bonnet temperatures than conventional layouts. This heat soak accelerates the degradation of plastic chain guides and can cause the hydraulic tensioner to lose oil pressure on hot restart, leading to chain rattle and eventual stretch [EM-INTERVIEW].
Independent specialists we've spoken to frequently recommend a chain inspection at 60,000 miles, regardless of what the service schedule indicates. If you hear a rattle on cold start that lasts more than 1–2 seconds, this is an early warning of tensioner failure. Addressing it early — replacing the tensioner and guides — costs a few hundred pounds. Ignoring it can lead to chain skip, bent valves, and a full engine rebuild or replacement [EM-INTERVIEW].
We cover the full failure mechanism on our M157 Timing Chain Adjuster Failure page. The key takeaway: the chain itself is robust, but the tensioner and guides are the weak points — and they're accelerated by the hot‑vee design.
The timing chain is not directly visible without removing the engine front cover, but you can check for chain wear indirectly:
For definitive confirmation, the front timing cover must be removed for visual inspection — a job that requires specialist knowledge. Use our Engine Number Location guide to confirm your engine variant.
Knowing whether the M157 uses a timing chain or belt matters because it affects maintenance planning, cost expectations, and failure risk assessment. A chain is generally more durable than a belt — it doesn't require routine replacement at a fixed mileage interval — but it is not maintenance‑free. The M157's chain tensioner and guides are known wear points, accelerated by the hot‑vee design.
If you're considering buying an M157‑powered car — such as an E63, CLS63, or S63 — check the service history for evidence of chain tensioner or guide replacement. Cars that have had this work done (especially with the revised tensioner) are far less likely to experience the catastrophic failure described on our failure page. Conversely, a car with no chain work and a cold‑start rattle should be approached with caution — the repair cost can exceed £3,000 at a specialist, and significantly more at a main dealer.
We also recommend reviewing our M157 Engine Page for the full reliability rating, replacement costs, and comparison with successors like the M178.
Every Figure SourcedUnverified numbers flagged, never guessed.
Last Verified February 2026Reviewed on a regular schedule, not left to go stale.
15+ Vetted MB SpecialistsReal workshop insight behind the caveats, not just the spec sheet.
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If you're hearing cold‑start rattle or suspect timing chain issues, get an honest diagnosis from our vetted specialist network.
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