2009 Mercedes-Benz A-Class diesel: common problems and MOT failures

What goes wrong more than usual on a 2009 Mercedes-Benz A-Class diesel?

Parts flagged at MOT more often on the 2009 Mercedes-Benz A-Class diesel than on all cars registered in 2009.

• Rigid brake pipes4.6× usual
  Mercedes-Benz A-Class

  33.2% All 2009 cars

  7.2%

  Failed outright at MOT: 5.8%, against 1.2% of all 2009 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.

• Shock absorbers2× usual
  Mercedes-Benz A-Class

  14.5% All 2009 cars

  7.1%

  Failed outright at MOT: 4.3%, against 2% of all 2009 cars. The rest were advisories or minor defects.

  Rough price £200–£300 (pair, average rear to front) ClickMechanic

  At the viewing: Push down hard on each corner. It should bounce once and settle. Look for oil on the shock absorber body.

• Flexible brake hoses3.3× usual
  Mercedes-Benz A-Class

  8.7% All 2009 cars

  2.6%

  Failed outright at MOT: 0.5%, against 0.4% of all 2009 cars. The rest were advisories or minor defects.

  Rough price £50–£200 our estimate

  At the viewing: Look for cracked or bulging rubber hoses behind the wheels and in the engine bay.

• Drive shaft (CV) joints2× usual
  Mercedes-Benz A-Class

  9.9% All 2009 cars

  4.9%

  Failed outright at MOT: 4.2%, against 2.3% of all 2009 cars. The rest were advisories or minor defects.

  Rough price £60–£350 our estimate

  At the viewing: Drive slowly on full steering lock in both directions and listen for clicking. Look for split rubber boots behind the front wheels.

• Side repeaters3.6× usual
  Mercedes-Benz A-Class

  5% All 2009 cars

  1.4%

  Failed outright at MOT: 3.6%, against 0.9% of all 2009 cars. The rest were advisories or minor defects.

  Rough price £10–£80 our estimate

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

Common 2009 Mercedes-Benz A-Class diesel MOT failures and advisories

The share of 2009 Mercedes-Benz A-Class diesel MOT tests where testers flagged each area, as a fail or an advisory. Rough prices are typical independent-garage costs.

• Brakes
  53% 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
  34% 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
  33% 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
  28% 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
  13% of testsRough price £15–£250

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

• Driveshafts and joints
  10% of testsRough price £60–£350

  At the viewing: On full steering lock, drive slowly and listen for clicking from the front wheels.

Known faults on the 2009 Mercedes-Benz A-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.

• Poor reliability: suspension and electrical faults

  All engines

  Faults were incredibly common, especially suspension and electrical ones, and the average repair bill was over £500.

  At the viewing: Get a pre-purchase inspection, listen for suspension knocks and test every electrical item.

  Source: What Car?: used Mercedes-Benz A-Class (2005-2012) reliability

Questions to ask the seller before buying a 2009 Mercedes-Benz A-Class diesel

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

1. What has gone wrong and been fixed?
2. Any recent work on the rigid brake pipes? (Flagged at MOT 4.6× as often on the 2009 Mercedes-Benz A-Class diesel as on other cars the same age.)
3. Any recent work on the shock absorbers? (Flagged at MOT 2× as often on the 2009 Mercedes-Benz A-Class diesel as on other cars the same age.)
4. Any recent work on the flexible brake hoses? (Flagged at MOT 3.3× as often on the 2009 Mercedes-Benz A-Class diesel as on other cars the same age.)
5. Can I see the service history and receipts for any big jobs?