Used car guide

2018 Mercedes-Benz S-Class: common problems and what to check

What gets flagged at MOT on 2018 Mercedes-Benz S-Classs, from 2,177 tests in 2025, plus known faults and what to look at before you buy one.

2,177MOT tests in 2025
91%pass first time (all 2018 cars: 81%)
9,800typical miles a year
4.7×the usual rate for ball joint

What stands out

Parts flagged at MOT more often on 2018 Mercedes-Benz S-Classs than on all cars registered in 2018.

  • Ball joint4.7× usual
    Mercedes-Benz S-Class
    6.1% All 2018 cars
    1.3%

    Failed outright at MOT: 1.8%, against 0.6% of all 2018 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.

Better than most

Tyre condition: 5.8% here, against 13.9% of all 2018 cars. Brake pads: 5.1% here, against 11% of all 2018 cars.

By area

The share of 2018 Mercedes-Benz S-Class MOT tests where testers flagged each area, as a fail or an advisory. Rough prices are typical independent-garage costs.

  • Tyres
    19% 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
    11% 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.

  • Suspension
    7% 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.

  • Wipers, windscreen and mirrors
    4% of testsRough price £15–£250

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

  • Lights and electrics
    3% of testsRough price £10–£80

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

  • Steering
    1% of testsRough price £100–£450

    At the viewing: On a straight road the steering wheel should sit straight. Feel for play or knocking when turning.

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Other years

YearMOT testsMost flagged
20192,195Tyres 19%
20172,265Tyres 21%
20162,634Tyres 24%
20152,124Tyres 23%
20141,572Tyres 21%
2013946Brakes 27%
20121,148Brakes 33%
2011883Brakes 32%
2010773Brakes 32%
2009753Brakes 37%
2008810Brakes 40%
20071,127Brakes 39%
2006883Brakes 38%
2004521Brakes 35%
2003522Brakes 34%

Where this comes from: the DVSA's anonymised results for every MOT test in Great Britain in 2025, counting tests of 2018 Mercedes-Benz S-Classs registered in 2018. "Flagged" includes advisories, so it isn't the same as a fail rate. How we score