1989 Mercedes-Benz Sl — MOT failures & pass rate
The 1989 Mercedes-Benz Sl passed 85.3% of its 877 recorded MOT tests. Against coupes & convertibles of a similar age (17.4% fail rate), the 1989 Sl comes out 2.7pp better. Failures cluster in lighting & signalling, brakes and suspension.
What the MOT record shows
No single area dominates — lighting & signalling (6.7%) and brakes (5.9%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are headlamp aim, service brake performance and non catalyst emissions — headlamp aim alone was recorded 41 times.
A 150k+ example is materially riskier than a 0-30k one: 31.7% versus 3.1%.
Emissions & environmental is the most common advisory, noted on 13.6% of tests — work that passed today but is likely due soon.
The trend is improving — the fail rate fell from 16.1% in 2021 to 10.5% in 2025, as the worst-kept examples leave the fleet.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 6.7% | 59 |
| 2 | Brakes | 5.9% | 52 |
| 3 | Suspension | 4.7% | 41 |
| 4 | Visibility | 3.8% | 33 |
| 5 | Body, structure & corrosion | 3.4% | 30 |
| 6 | Emissions & environmental | 3.0% | 26 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Headlamp aim | 41 |
| 2 | Service brake performance | 31 |
| 3 | Non catalyst emissions | 26 |
| 4 | Component mounting prescribed areas | 24 |
| 5 | Washers | 21 |
| 6 | Wipers | 16 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Emissions & environmental | 13.6% | 119 |
| 2 | Suspension | 13.0% | 114 |
| 3 | Brakes | 11.6% | 102 |
| 4 | Body, structure & corrosion | 9.6% | 84 |
| 5 | Tyres | 9.5% | 83 |
| 6 | Steering | 7.4% | 65 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 0-30k | 64 | 3.1% |
| 30-60k | 155 | 9.0% |
| 60-90k | 283 | 16.6% |
| 90-120k | 213 | 14.1% |
| 120-150k | 102 | 16.7% |
| 150k+ | 60 | 31.7% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 168 | 16.1% |
| 2022 | 189 | 15.9% |
| 2023 | 177 | 16.4% |
| 2024 | 181 | 14.4% |
| 2025 | 162 | 10.5% |
What to check before buying a 1989 Sl
The failure pattern for this year is specific enough to inspect against: lighting & signalling accounted for 6.7% of tests. Start there.
- Lighting & signalling (6.7% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Brakes (5.9% 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 (4.7% 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 1989 Mercedes-Benz Sls pass their MOT?
85.3% of the 877 1989 Mercedes-Benz Sl MOT tests in this dataset passed — a 14.7% fail rate.
What is the most common MOT failure on a 1989 Mercedes-Benz Sl?
Lighting & signalling, recorded in 6.7% of tests, followed by brakes (5.9%).
Does the 1989 Sl get worse with mileage?
Its MOT fail rate rises from 3.1% in the 0-30k band to 31.7% in the 150k+ band.
Methodology & source. Based on 877 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-27. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.