2009 Mercedes-Benz CLS diesel: common problems and MOT failures

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

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

• Rigid brake pipes3.1× usual
  Mercedes-Benz CLS

  22% All 2009 cars

  7.2%

  Failed outright at MOT: 5%, 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.

• Ball joint2.5× usual
  Mercedes-Benz CLS

  15.8% All 2009 cars

  6.3%

  Failed outright at MOT: 7%, against 3.4% of all 2009 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.

• Wheel bearings3.6× usual
  Mercedes-Benz CLS

  7.5% All 2009 cars

  2.1%

  Failed outright at MOT: 0.6%, against 0.8% of all 2009 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.

• Steering rack inner joints2.9× usual
  Mercedes-Benz CLS

  6.7% All 2009 cars

  2.3%

  Failed outright at MOT: 0%, against 0% of all 2009 cars. The rest were advisories or minor defects.

  Rough price £100–£450 our estimate

  At the viewing: On a straight road the steering wheel should sit straight. Listen for knocks when turning, and check the steering feels even.

Common 2009 Mercedes-Benz CLS diesel MOT failures and advisories

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

• Brakes
  38% 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
  36% 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
  34% 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
  26% 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
  15% 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.

• Exhaust and emissions
  11% of testsRough price £100–£1,200

  At the viewing: Look for black soot in the tailpipe, listen for blowing from the exhaust and check for engine or DPF warning lights.

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

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

1. Any recent work on the rigid brake pipes? (Flagged at MOT 3.1× as often on the 2009 Mercedes-Benz CLS diesel as on other cars the same age.)
2. Any recent work on the ball joint? (Flagged at MOT 2.5× as often on the 2009 Mercedes-Benz CLS diesel as on other cars the same age.)
3. Any recent work on the wheel bearings? (Flagged at MOT 3.6× as often on the 2009 Mercedes-Benz CLS diesel as on other cars the same age.)
4. Can I see the service history and receipts for any big jobs?