Owners track a running change during 2012 on both cooling (single vs dual circuit) and the timing chain, with one seller pointing to an engine-number cutoff of 22333 for the older-style chain. Multiple high-mileage M157 owners report the later multi-link chain is trouble-free, with preventive tensioner updates and a check valve, though loud tapping can signal worn tensioners and guides.
Single vs dual-circuit cooling and timing-chain evolution
Mercedes-Benz E63 AMG (W212) · mechanical