1987 Mercedes-Benz 420 — MOT failures & pass rate
Across 868 MOT tests analysed for the 1987 Mercedes-Benz 420, the most common recorded failure areas were lighting & signalling, brakes and suspension. Its pass rate of 84.5% was above the average for cars of a similar age (80.5%). Higher-mileage examples failed more often — 19.2% in the 150k+ group versus 6.5% in the 30-60k group.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 8.8% | 76 |
| 2 | Brakes | 6.2% | 54 |
| 3 | Suspension | 5.5% | 48 |
| 4 | Body, structure & corrosion | 3.6% | 31 |
| 5 | Visibility | 3.2% | 28 |
| 6 | Emissions & environmental | 3.2% | 28 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Ball joint dust cover | 48 |
| 2 | Headlamp aim | 45 |
| 3 | Service brake performance | 39 |
| 4 | Component mounting prescribed areas | 30 |
| 5 | Non catalyst emissions | 26 |
| 6 | Wipers | 19 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Suspension | 20.3% | 176 |
| 2 | Emissions & environmental | 13.1% | 114 |
| 3 | Brakes | 12.7% | 110 |
| 4 | Body, structure & corrosion | 10.0% | 87 |
| 5 | Steering | 9.4% | 82 |
| 6 | Tyres | 9.0% | 78 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 30-60k | 107 | 6.5% |
| 60-90k | 265 | 11.7% |
| 90-120k | 261 | 19.9% |
| 120-150k | 117 | 21.4% |
| 150k+ | 99 | 19.2% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 184 | 16.9% |
| 2022 | 183 | 13.7% |
| 2023 | 172 | 16.3% |
| 2024 | 169 | 16.0% |
| 2025 | 160 | 15.0% |
What to check before buying a 1987 420
Before buying a 1987 Mercedes-Benz 420, focus on the areas it most often fails on. Lighting & signalling accounted for 8.8% of tests for this year.
- Lighting & signalling (8.8% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Brakes (6.2% of tests): Pads/discs are routine wear; binding, imbalance or corroded pipes are more serious — test for pulling under braking. Typical repair: £100–£350 per axle.
- Suspension (5.5% of tests): Worn drop links, bushes, springs or shocks — listen for knocks over bumps and check for uneven tyre wear. Typical repair: £150–£450 per corner.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
How many 1987 Mercedes-Benz 420s pass their MOT?
84.5% of the 868 1987 Mercedes-Benz 420 MOT tests in this dataset passed — a 15.6% fail rate.
What is the most common MOT failure on a 1987 Mercedes-Benz 420?
Lighting & signalling, recorded in 8.8% of tests, followed by brakes (6.2%).
Does the 1987 420 get worse with mileage?
Its MOT fail rate rises from 6.5% in the 30-60k band to 19.2% in the 150k+ band.
Methodology & source. Based on 868 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-01. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.