Why it's a good car
The 2012 ML350 is the third-generation M-Class — the W166, a clean-sheet redesign for 2012. Mercedes used the launch to retire the troubled M272 V6, whose balance-shaft gear defect turned a lot of earlier MLs into expensive problems, and bring in the all-new direct-injected M276 3.5-litre V6 (around 302 hp). That single change matters: the specific failure that defined the previous generation is gone. It is paired with the 7G-Tronic Plus seven-speed automatic and full-time 4MATIC all-wheel drive, and it rides on steel coil springs as standard, with AIRMATIC air suspension only as an option.
Does it have a timing belt or a timing chain?
A timing chain. The M276 V6 is chain-driven, so there is no scheduled timing-belt job. The thing to listen for instead is a brief rattle from the camshaft-adjuster and timing-chain area on a cold start — a known M276 concern that is tied closely to oil-change discipline. A clean, quiet cold start is exactly what you want.
The things to check before you buy
- Cold-start rattle Start it stone cold and listen at the front of the engine for the first several seconds. A quick settle is normal; a lingering metallic rattle points to the cam adjuster or timing chain, and that is the expensive end of this engine.
- Transmission behaviour The seven-speed is reliable when its fluid has actually been serviced — ignore the sealed-for-life marketing. You want clean, prompt shifts with no slip or flare.
- Air conditioning The A/C compressor is a common failure on hot-climate examples; confirm it blows genuinely cold.
- Suspension type Confirm whether it is on standard steel coils (simple and cheap) or the optional AIRMATIC air suspension (expensive) by looking for a coil spring versus a rubber air bellows at the corners.
- Intake-manifold tumble-flap motor A documented M276 item that usually throws a check-engine light before it strands anyone.
- Proper diagnostics These need a Mercedes-capable scan tool — not just a generic code reader — to read the transmission, SRS/airbag, and air-suspension modules.
- Open recalls Confirm any outstanding Mercedes recalls were completed; the dealer performs them free.
What would make you walk
- A rattle that won't clear A loud, sustained cold-start rattle, or any chain-area knock under acceleration.
- Coolant in the oil Milky, cream-coloured residue under the oil cap.
- A tired transmission Slip, flare, or harsh engagement despite a recent fluid service.
- An SRS fault An airbag or seatbelt warning light that will not clear.