2003 Mercedes-Benz C-Class diesel: common problems and MOT failures

What goes wrong more than usual on a 2003 Mercedes-Benz C-Class diesel?

Parts flagged at MOT more often on the 2003 Mercedes-Benz C-Class diesel than on all cars registered in 2003.

• Ball joint2.7× usual
  Mercedes-Benz C-Class

  17.2% All 2003 cars

  6.4%

  Failed outright at MOT: 9%, against 3% of all 2003 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.

• Sub-frame2.5× usual
  Mercedes-Benz C-Class

  11.3% All 2003 cars

  4.6%

  Failed outright at MOT: 0.2%, against 0.3% of all 2003 cars. The rest were advisories or minor defects.

  Rough price £300–£1,000 our estimate

  At the viewing: Look underneath at the frame the suspension bolts to. Flaky rust or holes are expensive to fix.

• Diesel smoke emissions6.9× usual
  Mercedes-Benz C-Class

  5.5% All 2003 cars

  0.8%

  Failed outright at MOT: 5.2%, against 0.6% of all 2003 cars. The rest were advisories or minor defects.

  Rough price £175–£900 (catalytic converter) ClickMechanic

  At the viewing: Look for smoke when revving the warm engine and for engine or DPF warning lights.

• Wheel bearings2.2× usual
  Mercedes-Benz C-Class

  8.3% All 2003 cars

  3.8%

  Failed outright at MOT: 0.6%, against 1.3% of all 2003 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.

• Anti-roll bar bushes and joints3.1× usual
  Mercedes-Benz C-Class

  5.3% All 2003 cars

  1.7%

  Failed outright at MOT: 1.3%, against 0.4% of all 2003 cars. The rest were advisories or minor defects.

  Rough price £100–£280 (pair of drop links) Checkatrade

  At the viewing: Drive slowly over bumps and listen for a knock or rattle from the front. Worn anti-roll bar links are a cheap fix.

Common 2003 Mercedes-Benz C-Class diesel MOT failures and advisories

The share of 2003 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.

• Suspension
  56% 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.

• Brakes
  45% 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.

• Lights and electrics
  38% of testsRough price £10–£80

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

• 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.

• 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.

• Exhaust and emissions
  13% 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 2003 Mercedes-Benz C-Class 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 ball joint? (Flagged at MOT 2.7× as often on the 2003 Mercedes-Benz C-Class diesel as on other cars the same age.)
2. Any recent work on the sub-frame? (Flagged at MOT 2.5× as often on the 2003 Mercedes-Benz C-Class diesel as on other cars the same age.)
3. Any recent work on the diesel smoke emissions? (Flagged at MOT 6.9× as often on the 2003 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?