2017 Smart Forfour: common problems and MOT failures

What goes wrong more than usual on a 2017 Smart Forfour?

Parts flagged at MOT more often on the 2017 Smart Forfour than on all cars registered in 2017.

• Exhaust emissions (catalyst)7.3× usual
  Smart Forfour

  2.2% All 2017 cars

  0.3%

  Failed outright at MOT: 2.2%, against 0.3% of all 2017 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.

• Ball joint1.8× usual
  Smart Forfour

  2.7% All 2017 cars

  1.5%

  Failed outright at MOT: 1.9%, against 0.7% of all 2017 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.

• Brake lights2× usual
  Smart Forfour

  2.2% All 2017 cars

  1.1%

  Failed outright at MOT: 2.1%, against 0.9% of all 2017 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 2017 Smart Forfour MOT failures and advisories

The share of 2017 Smart Forfour MOT tests where testers flagged each area, as a fail or an advisory. Rough prices are typical independent-garage costs.

• 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.

• Brakes
  19% 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
  8% 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
  8% of testsRough price £15–£250

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

• Suspension
  8% 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.

• Exhaust and emissions
  3% 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 2017 Smart Forfour

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

1. Any recent work on the exhaust emissions (catalyst)? (Flagged at MOT 7.3× as often on the 2017 Smart Forfour as on other cars the same age.)
2. Any recent work on the ball joint? (Flagged at MOT 1.8× as often on the 2017 Smart Forfour as on other cars the same age.)
3. Any recent work on the brake lights? (Flagged at MOT 2× as often on the 2017 Smart Forfour as on other cars the same age.)
4. Can I see the service history and receipts for any big jobs?