Mercedes-Benz B-Klasse 246 B 180 CDI, 109 PS, 7-speed dual-clutch (2012–2014)

Research for this car

• Engine guide Mercedes OM651 2.1 diesel (C 220 CDI, E 250 CDI, Sprinter): problems, costs and what to check

  Durable when maintained, but check the cold start chain rattle, early injectors and the 2014 tensioner seal before you buy.

• 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 a Mercedes dealer or a diesel specialist to read the cam phase offset (the timing gap between camshaft and crankshaft) with XENTRY, the Mercedes diagnostic tool. Check for codes P0016 and P0017. A plain OBD2 scanner may miss the offset. Bad: a rattle, a stored P0016 or P0017, or a large offset. A jumped chain can destroy the engine.
2. Coolant (no scanner). Check the coolant level when the engine is cold, and check it again after a few weeks. Ask a dealer whether service action 1204P59A93 was done on the cylinder head coolant connection. Bad: a falling level or no record of the work.
3. Tensioner seal recall (VIN check). For cars built February to November 2014, ask a Mercedes dealer to check the VIN for the seal ring fix. Bad: no record of the fix.
4. Emissions software update (VIN check). Ask a Mercedes dealer to check the VIN for the emissions software update. Bad: no record of the update.
5. Oil and service history (no scanner). Ask for oil change records. Long gaps between oil changes, short trips and poor oil all 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