2012 Mercedes-Benz E-Class diesel: common problems and MOT failures

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

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

• Rigid brake pipes4.5× usual
  Mercedes-Benz E-Class

  22.7% All 2012 cars

  5%

  Failed outright at MOT: 4.2%, 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.

• Wheel bearings3.8× usual
  Mercedes-Benz E-Class

  5.3% All 2012 cars

  1.4%

  Failed outright at MOT: 0.2%, against 0.5% of all 2012 cars. The rest were advisories or minor defects.

  Rough price £120–£300 (one bearing) ClickMechanic

  At the viewing: Listen for a hum or growl that changes as you steer at speed.

• Link ball joint covers2.9× usual
  Mercedes-Benz E-Class

  5.8% All 2012 cars

  2%

  Failed outright at MOT: 2.1%, 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 light1.7× usual
  Mercedes-Benz E-Class

  2.9% All 2012 cars

  1.7%

  Failed outright at MOT: 2.9%, 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.

Common 2012 Mercedes-Benz E-Class diesel MOT failures and advisories

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

• Brakes
  39% 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.

• Tyres
  32% 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.

• Suspension
  28% 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
  14% of testsRough price £10–£80

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

• Oil and fluid leaks
  7% of testsRough price £80–£600

  At the viewing: Look under the engine and on the ground where the car is usually parked for fresh oil or fluid.

• Wipers, windscreen and mirrors
  5% of testsRough price £15–£250

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

Known faults on the 2012 Mercedes-Benz E-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.

• Timing chains on diesels

  Diesel

  The diesel timing chains won't last forever. A rattle on start-up is the warning sign.

  At the viewing: Start the engine from cold and listen for a rattle.

  Source: Parkers: used Mercedes E-Class 2009-2016 review

• Water pump and coolant leaks

  All engines

  The water pump is a common failure, and diesels can leak coolant around the EGR cooler.

  At the viewing: Listen for whining from the engine, and look for dried coolant around it.

  If it needs doing: Water pump, about £115–£375. ClickMechanic

  Source: Parkers: used Mercedes E-Class 2009-2016 review

• 7G-Tronic automatic

  Automatic

  The automatic gearbox needs looking after.

  At the viewing: Check the changes are smooth with no odd noises, and look for gearbox servicing in the history.

  If it needs doing: Gearbox sensor or solenoid, about £200–£500. ClickMechanic

  Source: Parkers: used Mercedes E-Class 2009-2016 review

• Oil cooler leak (early E350 V6 diesel)

  E350 V6 diesel

  The oil cooler seals can leak on early V6 diesels, and the repair takes a lot of labour.

  At the viewing: Look for oil around the top and front of the engine.

  Source: Parkers: Mercedes E-Class saloon (2009-2016) used review

• Rust on the rear subframe

  All engines

  The rear subframe and axle rust, especially where the roads are salted.

  At the viewing: Look underneath at the rear subframe.

  Source: Parkers: Mercedes E-Class saloon (2009-2016) used review

• Particulate filter (diesel)

  Diesel

  The particulate filter will fail on cars that mostly do short journeys.

  At the viewing: Ask what journeys it does, and watch for warning lights.

  Source: Parkers: Mercedes E-Class saloon (2009-2016) used review

• Electrical and sensor faults

  All engines

  Electrical faults range from oxygen and crank sensors to full ECU failure. Cracked air hoses can cause limp mode.

  At the viewing: Make sure no warning lights are on and test the electrics.

  Source: Parkers: Mercedes E-Class saloon (2009-2016) used review

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

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

1. Has the timing chain ever been replaced?
2. Has the water pump been replaced?
3. Has the gearbox oil been changed?
4. Any recent work on the rigid brake pipes? (Flagged at MOT 4.5× as often on the 2012 Mercedes-Benz E-Class diesel as on other cars the same age.)
5. Any recent work on the wheel bearings? (Flagged at MOT 3.8× as often on the 2012 Mercedes-Benz E-Class diesel as on other cars the same age.)
6. Any recent work on the link ball joint covers? (Flagged at MOT 2.9× as often on the 2012 Mercedes-Benz E-Class diesel as on other cars the same age.)