2015 Mercedes-Benz C-Class diesel: common problems and MOT failures

What goes wrong more than usual on a 2015 Mercedes-Benz C-Class diesel?

Parts flagged at MOT more often on the 2015 Mercedes-Benz C-Class diesel than on all cars registered in 2015.

• Ball joint3× usual
  Mercedes-Benz C-Class

  8.9% All 2015 cars

  3%

  Failed outright at MOT: 3.3%, against 1.7% of all 2015 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 light2.1× usual
  Mercedes-Benz C-Class

  3.2% All 2015 cars

  1.5%

  Failed outright at MOT: 3.2%, against 1.5% of all 2015 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.

Common 2015 Mercedes-Benz C-Class diesel MOT failures and advisories

The share of 2015 Mercedes-Benz C-Class diesel 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
  21% 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
  17% 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
  7% 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
  2% of testsRough price £80–£250

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

Known faults on the 2015 Mercedes-Benz C-Class diesel

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.

• Diesel emissions system faults

  Diesel

  Particulate filter, NOx sensor and AdBlue problems are the main worry on diesels, especially ones used for short trips.

  At the viewing: Watch for emissions or AdBlue warnings on the dash, and ask what journeys it’s done.

  Source: Parkers: Mercedes C-Class (2014-2021) used review

• Air suspension

  Cars with air suspension

  Cars with air suspension can develop expensive faults that need a specialist.

  At the viewing: Check the car sits level all round, look for uneven front tyre wear, and watch for suspension warnings.

  Source: Parkers: Mercedes C-Class (2014-2021) used review

• Automatic gearbox behaviour

  Automatic

  Some automatics shift inconsistently.

  At the viewing: Drive through every gear at different speeds. Any odd or jerky changes should be priced in or a reason to walk away.

  Source: Parkers: Mercedes C-Class (2014-2021) used review

Questions to ask the seller before buying a 2015 Mercedes-Benz C-Class diesel

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

1. Have there been any AdBlue or particulate filter warnings?
2. Any recent work on the ball joint? (Flagged at MOT 3× as often on the 2015 Mercedes-Benz C-Class diesel as on other cars the same age.)
3. Any recent work on the engine warning light? (Flagged at MOT 2.1× as often on the 2015 Mercedes-Benz C-Class diesel as on other cars the same age.)
4. Can I see the service history and receipts for any big jobs?