Used car guide

2021 Mercedes-Benz B-Class: common problems and MOT failures

What MOT testers find on the Mercedes-Benz B-Class first registered in 2021: we looked at the 3,631 MOTs these cars had during 2023–2025. Plus known faults and what to look at before you buy one.

3,631MOTs of 2021 cars, done in 2023–2025
91%pass first time (all 2021 cars: 87%)
6,400typical miles a year
20%had tyres flagged

Common 2021 Mercedes-Benz B-Class MOT failures and advisories

The share of 2021 Mercedes-Benz B-Class MOT tests where testers flagged each area, as a fail or an advisory. Rough prices are typical independent-garage costs.

  • Tyres
    20% 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
    5% 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.

  • 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.

  • Seats and seatbelts
    2% of testsRough price £80–£250

    At the viewing: Pull each seatbelt sharply. It should lock, and retract cleanly.

  • Suspension
    1% 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.

Questions to ask the seller before buying a 2021 Mercedes-Benz B-Class

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

  1. Can I see the service history and receipts for any big jobs?

Looking at a Mercedes-Benz B-Class?

Check the actual car: its own MOT history, mileage and what to ask the seller. Free, no sign-up.

Other years

Every year of the Mercedes-Benz B-Class compared

YearMOT testsMost flagged
2026–Too new for MOT data
2025–Too new for MOT data
2024–Too new for MOT data
2023–Too new for MOT data
20221,424Tyres 19%
20208,747Tyres 23%
20191,758Tyres 24%
201811,521Tyres 29%
201716,941Tyres 30%
201615,928Tyres 31%
201516,859Tyres 31%
201424,593Tyres 32%
201321,133Tyres 32%
201217,251Tyres 31%
201110,635Brakes 40%
201013,626Brakes 42%
200913,002Brakes 47%
200810,481Brakes 50%
20078,076Brakes 48%
20066,099Brakes 49%
20051,264Brakes 48%

Where this comes from: the DVSA's anonymised results for every MOT test done in Great Britain during 2023–2025, counting the MOTs of Mercedes-Benz B-Class cars first registered in 2021. "Flagged" includes advisories, so it isn't the same as a fail rate. How we score