Why it's a good car
The 2014 E350 is the W212 facelift, and it has the right engine: the M276 3.5-liter V6 (about 302 hp) that replaced the earlier M272, whose balance-shaft defect ate engines from the inside. It is paired with the 722.9 7G-Tronic Plus seven-speed automatic and was built as a genuine long-distance car — high highway mileage is not the alarm it first appears to be. And on the North American rear-wheel-drive E350 sedan, the suspension is conventional steel springs, not the expensive air suspension fitted to some other E-Class variants — so there is no air-strut bill lurking on this specific car.
Does it have a timing belt or a timing chain?
A timing chain. The M276 is chain-driven, so there is no belt to replace. The thing to listen for instead is a brief rattle from the camshaft-adjuster and timing-chain area on a cold start; a clean, quiet cold start is exactly what you want.
The things to check before you buy
- Cold-start rattle With the engine stone cold, listen at the front for the first few seconds. A quick settle is normal; a sustained metallic rattle points to worn camshaft adjusters.
- Engine wiring harness / cam-sensor oil intrusion The camshaft-position-sensor seals on this engine can seep oil that wicks along the harness toward the ECU. Caught early it is a seal-and-clean job; ignored, it can destroy the harness and computer and become the most expensive failure on the car. Have a mechanic look at the connectors with the engine cover off — this is non-negotiable.
- Transmission behavior The 722.9 conductor plate (its electronic valve-body brain) is a known wear item. You want clean shifts cold and warm — no harsh 1–2, no long delay engaging Drive, no limp mode.
- Proper diagnostics These need a Mercedes-capable scan tool, not just a generic reader, to see the transmission and SRS systems where the real faults hide.
- Ordinary age items The plastic coolant expansion tank cracks with age, spark plugs come due, and blower regulators and rear shock mounts are common nuisance items.
What would make you walk
- Oil in the harness Oil visible at the camshaft-sensor connectors or wicking into the engine wiring harness.
- Coolant in the oil Cream or mayonnaise residue under the oil cap.
- A rattle that won't clear A sustained cold-start rattle or a chain-area knock under load.
- A tired transmission Harsh, flaring, or delayed shifts, or limp mode.