2021 BMW 420: common problems and what to check
What gets flagged at MOT on 2021 BMW 420s, from 341 tests in 2025, plus known faults and what to look at before you buy one.
Small sample: only 341 of these were MOT tested in 2025, so treat the percentages as rough. The known faults below don't depend on it.
What gets flagged at MOT
The share of 2021 BMW 420 MOT tests where testers flagged each area, as a fail or an advisory. Rough prices are typical independent-garage costs.
- Tyres26% 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.
- Brakes15% 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 mirrors4% of testsRough price £15–£250
At the viewing: Check for chips in the driver's view, and test the wipers and washers.
- Lights and electrics4% of testsRough price £10–£80
At the viewing: Ask a friend to check every light, including brake lights and indicators, while you operate them.
- Suspension2% 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.
- Seats and seatbelts1% of testsRough price £80–£250
At the viewing: Pull each seatbelt sharply. It should lock, and retract cleanly.
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Other years
| Year | MOT tests | Most flagged |
|---|---|---|
| 2020 | 3,067 | Tyres 26% |
| 2019 | 7,511 | Tyres 28% |
| 2018 | 10,218 | Tyres 28% |
| 2017 | 11,165 | Tyres 29% |
| 2016 | 11,181 | Tyres 29% |
| 2015 | 10,034 | Tyres 31% |
| 2014 | 7,599 | Tyres 31% |
| 2013 | 537 | Tyres 33% |
Where this comes from: the DVSA's anonymised results for every MOT test in Great Britain in 2025, counting tests of 2021 BMW 420s registered in 2021. "Flagged" includes advisories, so it isn't the same as a fail rate. How we score