Mercedes-Benz B-Klasse 246/242 facelift B 250, 211 PS, 7-speed dual-clutch (2014–2018)

Research for this car

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  A decent engine when the oil is changed on time, but a cold-start rattle or unusual engine noise on a 2015 car should stop the deal.

• Gearbox guide Mercedes 7G-DCT dual-clutch (724.0): problems, costs and what to check

  Smooth when serviced, but early cars judder and mechatronic or clutch repairs are costly. Buy on oil history and a cold test drive.

Known issues for this car

Before you buy this car

From the engine guide

1. Timing chain (scanner needed). Start the engine cold and listen for a metallic rattle for 1-3 seconds. Ask for Xentry live cam data and check for codes P0016, P0017 and P0011. Bad: a rattle, any of those codes, or a chain reported as slack. A jumped chain can destroy the engine.
2. Camshaft (no scanner). For a 2015 car, listen for unusual engine noise at idle and under load, and check for power loss and rough running. Bad: a noisy engine, or power loss and rough running on the test drive.
3. Thermostat (scanner needed). From cold, the engine should reach about 80 C within 10 minutes, and the live reading should sit between 95 and 105 C. Read codes P0128 or P1296. Bad: a temperature that stays low, overheating, or either code.
4. Coolant (no scanner). Check the level when cold and again after a few weeks. Bad: a falling level or coolant stains around the expansion tank.
5. Injectors and intake valves (scanner needed). Look for rough idle, misfires, power loss and higher fuel use. Bad: a misfire code or a rough idle.
6. Oil and service history (no scanner). Ask for oil change records. Long gaps between changes and short trips speed up chain wear. Bad: long gaps or no records.

From the gearbox guide

1. Clutch check (needs a scanner). Start cold, creep and pull away in 1st and 2nd, and hold on a hill. Judder, slip, or a vibration at a standstill with the brake on points to worn clutch plates. Read the clutch touch points (Kisspoint) in XENTRY, Mercedes' diagnostic software; K1 odd gears, K2 even. A value past the threshold means a new clutch.
2. Mechatronic scan (needs a scanner). Read all transmission codes, not just engine codes. A clean scan does not prove health: one 2014 CLA had no codes but still shook and once dropped into neutral. A stored code, a red warning or a limp-home episode means a control unit job.
3. Auxiliary oil pump warning. Ask whether a "Transmission malfunction" message appeared and cleared after gentle driving. A message that stays, or a "stop vehicle" warning, points to the auxiliary pump or control unit. Scan for codes.
4. Cold and warm road test. Drive in stop-go traffic and lift off in 1st and 2nd. Jerking that stays when warm, or shifts that hang under load, points to software, adaptation or clutch wear. Ask for the last software update.
5. Oil and filter records. Ask for invoices for the fluid and both filters, and for the adaptation reset after the last oil change. No record, black oil or metal fuzz on the drain plug means walk away or budget for a service. Dirty oil damages the control unit.

Running costs

ADAC figures for 15,000 km a year over 60 months

ADAC versions