BMW 420 MOT Failures
An analysis of 535,772 real DVSA MOT tests on the BMW 420 — what fails, how often, and how that compares to every other car on UK roads.
Where the BMW 420 fails its MOT
The single biggest MOT failure point on the BMW 420 is any fracture or welding defect on a wheel — this model is 18 times more likely to fail on this item than the average car on UK roads. That makes it a significant weak point for anyone buying or owning this model. Across 535,772 MOT tests, 0.18% of all BMW 420 tests recorded this as a failure.
Wheel-related failures include cracked alloys, damaged wheel studs, and bearing play. Listen for rumbling at speed (wheel bearings) and check for any visible cracks around alloy spokes.
Other notable weak points include tyre wear or damage (12x the fleet average), window tint too dark (7.9x the fleet average), electrical wiring fault (14x the fleet average), and headlight fault (11x the fleet average). These ratios compare the BMW 420's failure rate on each item against the national average for all cars tested — a ratio of 10x means this model fails ten times more often than a typical car.
The failures span 6 categories: Wheels, Tyres, Wipers & Windscreen, Lights & Electrics, Suspension and others. If you're inspecting a BMW 420 before purchase, these are the areas to focus on — and if any have been flagged as advisories on a previous MOT, they're likely to become failures in the near future.
How failures change with mileage
The BMW 420's weak points shift as the car covers more miles. Understanding these patterns helps you know what to expect — and what to budget for — at each stage of ownership.
Under 60,000 miles
At this mileage, most failures are either design-related or caused by age rather than wear. Components like bushes and drop links may not have been replaced yet, and original-fit parts can deteriorate even on low-mileage cars that spend a lot of time sitting.
For the BMW 420 specifically, the DVSA data shows the most common failures at this mileage are electrical wiring fault (14x the average) and window tint too dark (7.3x). brake fluid warning light illuminated or defective (7.1x) and fluid leak (5.7x) also appear frequently.
60,000 to 100,000 miles
This is where routine wear items start to show up. Brake components, tyres, and exhaust parts have done serious work by this point. Cars that have been well serviced will show fewer of these failures — this mileage band is where good maintenance really separates the well-kept from the neglected.
For the BMW 420 specifically, the DVSA data shows the most common failures at this mileage are any fracture or welding defect on a wheel (18x the average) and suspension component damaged or corroded (9.7x). window tint too dark (7.9x) and headlight fault (7.9x) also appear frequently.
Over 100,000 miles
High-mileage cars accumulate failures across multiple systems. The key question isn't whether things will need doing — they will — but whether the car has been maintained well enough to keep on top of them. Look for a consistent service history and recent MOT passes with minimal advisories.
For the BMW 420 specifically, the DVSA data shows the most common failures at this mileage are headlight fault (11x the average) and any fracture or welding defect on a wheel (7.3x). tyre wear or damage (6.0x) and tyre wear or damage also appear frequently.
The shift from electrical wiring fault at lower mileages to headlight fault at higher mileages is typical — early failures tend to be design or factory-related, while high-mileage failures reflect accumulated mechanical wear. A car that's been well maintained will usually dodge the worst of both.
What to check before buying a BMW 420
Based on the MOT failure data and known issues above, here's what to prioritise when inspecting a BMW 420:
Wheels — check for any fracture or welding defect on a wheel, wheel with a loose or missing wheel nut, bolt o.... Tyres — check for tyre wear or damage. Wipers & Windscreen — check for window tint too dark. Lights & Electrics — check for electrical wiring fault, headlight fault.
Always check the car's full MOT history for patterns — recurring advisories often become failures within 12 months. Enter any reg into our free car check to see the complete picture.
Looking at a specific BMW 420?
Enter the reg to see its full MOT history, mileage records, write-off status, and finance checks.
BMW 420 MOT FAQs
What are the most common MOT failures on a BMW 420?
Based on 535,772 DVSA MOT tests, the most common failure is any fracture or welding defect on a wheel — at 18x the national fleet average. Other frequent failures include tyre wear or damage and window tint too dark.
Is the BMW 420 reliable based on MOT data?
The BMW 420 has 10 categories where it fails more often than average. The main concern is any fracture or welding defect on a wheel. Always check a specific car's full history before buying.
What MOT failures should I expect at high mileage?
Above 100,000 miles, the BMW 420 most commonly fails on headlight fault and any fracture or welding defect on a wheel. Under 60,000 miles, the main issues are electrical wiring fault and window tint too dark.
How do I check a BMW 420's MOT history?
Enter the registration number into our free car check above. You'll see every MOT test result, advisories and failures, mileage readings, write-off status, and finance checks.
MOT failure data sourced from DVSA bulk test records via data.gov.uk. Ratios compare this model's failure rate against the national fleet average. Known issues sourced from manufacturer bulletins, specialist workshops, and verified owner reports.