2012 Mercedes-Benz B-Class: common problems and MOT failures

What goes wrong more than usual on a 2012 Mercedes-Benz B-Class?

Parts flagged at MOT more often on the 2012 Mercedes-Benz B-Class than on all cars registered in 2012.

• Rigid brake pipes2.3× usual
  Mercedes-Benz B-Class

  11.7% All 2012 cars

  5%

  Failed outright at MOT: 2.3%, against 0.8% of all 2012 cars. The rest were advisories or minor defects.

  Rough price £100–£400 our estimate

  At the viewing: Ask to see underneath, or check the MOT advisories: corroded brake or fuel pipes get worse every year and fail the MOT when they do.

• Link ball joint covers3.9× usual
  Mercedes-Benz B-Class

  7.8% All 2012 cars

  2%

  Failed outright at MOT: 4.2%, against 1.1% of all 2012 cars. The rest were advisories or minor defects.

  Rough price £60–£150 (one joint) ClickMechanic

  At the viewing: Listen for knocking over bumps and check the rubber boots behind the wheels aren't split.

• Engine warning light1.9× usual
  Mercedes-Benz B-Class

  3.2% All 2012 cars

  1.7%

  Failed outright at MOT: 3.2%, against 1.7% of all 2012 cars. The rest were advisories or minor defects.

  Rough price £10–£80 our estimate

  At the viewing: Ask a friend to check every light while you work the switches: indicators, brake lights, fog lights and reversing lights.

• Wheels1.7× usual
  Mercedes-Benz B-Class

  2.8% All 2012 cars

  1.6%

  Failed outright at MOT: 1.7%, against 0.5% of all 2012 cars. The rest were advisories or minor defects.

  Rough price £70–£150 our estimate

  At the viewing: Check the tread on all four tyres, including the inside edges, and look for cracks or bulges.

Petrol or diesel: does it make a difference?

The same figures for each fuel on its own. Check which one the car you're looking at is: it's on the logbook and in its MOT history.

Common 2012 Mercedes-Benz B-Class MOT failures and advisories

The share of 2012 Mercedes-Benz B-Class MOT tests where testers flagged each area, as a fail or an advisory. Rough prices are typical independent-garage costs.

• Tyres
  31% of testsRough price £70–£150

  At the viewing: Check the tread on all four tyres, including the inside edges, and look for cracks or bulges.

• Brakes
  29% of testsRough price £150–£350

  At the viewing: Look for a lip on the disc edges and feel for judder or pulling when braking firmly from about 40mph.

• Suspension
  25% of testsRough price £120–£400

  At the viewing: Listen for knocks over speed bumps, and look behind each front wheel for a snapped coil spring.

• Lights and electrics
  15% of testsRough price £10–£80

  At the viewing: Ask a friend to check every light, including brake lights and indicators, while you operate them.

• Wipers, windscreen and mirrors
  6% of testsRough price £15–£250

  At the viewing: Check for chips in the driver's view, and test the wipers and washers.

• Seats and seatbelts
  3% of testsRough price £80–£250

  At the viewing: Pull each seatbelt sharply. It should lock, and retract cleanly.

Known faults on the 2012 Mercedes-Benz B-Class

Reported by owners, mechanics and buying guides for this model and age. Check which engine the car has, as some apply to one engine only.

• Many recalls (21)

  All engines

  Recalls covered automatic gearbox faults, rear seat backrests, engine failures (2015), fuel leaks, brakes, airbags, air con, adaptive cruise and headlights stuck on main beam.

  At the viewing: Ask a Mercedes dealer to check the VIN for outstanding recalls.

  Source: Auto Express: used Mercedes B-Class (Mk2, 2011-2019) review

• Dual-clutch gearbox surging

  Automatic

  The dual-clutch automatic can surge and lose drive.

  At the viewing: Drive in slow traffic and pull away several times.

  Source: Auto Express: used Mercedes B-Class (Mk2, 2011-2019) review

• Starter motor wear

  Cars with stop-start

  The stop-start system can shorten the starter motor’s life.

  At the viewing: Listen for a slow or noisy restart at junctions.

  Source: Auto Express: used Mercedes B-Class (Mk2, 2011-2019) review

Questions to ask the seller before buying a 2012 Mercedes-Benz B-Class

Ask before you travel to see it. A seller who knows the car will have answers, and receipts.

1. Have all the recalls been done? Can a Mercedes dealer confirm from the VIN?
2. Any recent work on the rigid brake pipes? (Flagged at MOT 2.3× as often on the 2012 Mercedes-Benz B-Class as on other cars the same age.)
3. Any recent work on the link ball joint covers? (Flagged at MOT 3.9× as often on the 2012 Mercedes-Benz B-Class as on other cars the same age.)
4. Any recent work on the engine warning light? (Flagged at MOT 1.9× as often on the 2012 Mercedes-Benz B-Class as on other cars the same age.)
5. Can I see the service history and receipts for any big jobs?