1990 Mercedes-Benz Sl — MOT failures & pass rate
430 MOT tests on the 1990 Mercedes-Benz Sl are in this dataset, and 86.1% of them passed. That is 4.3 percentage points better than coupes & convertibles of a similar age, which fail at 18.3%. Failures cluster in lighting & signalling, suspension and brakes.
What the MOT record shows
One area stands out: lighting & signalling, recorded in 9.1% of tests against 4.2% for the next-worst category.
At component level the recurring items are headlamp aim, non catalyst emissions and individual direction indicators — headlamp aim alone was recorded 11 times.
Mileage is the strongest signal on the record: 11.4% of 0-30k cars fail, rising to 20.5% once past 120-150k.
Brakes is the most common advisory, noted on 22.1% of tests — work that passed today but is likely due soon.
The trend is worsening — 11.2% of tests failed in 2021 against 15.3% in 2025, the usual pattern as a fleet ages.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 9.1% | 39 |
| 2 | Suspension | 4.2% | 18 |
| 3 | Brakes | 4.0% | 17 |
| 4 | Visibility | 3.7% | 16 |
| 5 | Emissions & environmental | 3.3% | 14 |
| 6 | Steering | 1.4% | 6 |
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 | 11 |
| 2 | Non catalyst emissions | 11 |
| 3 | Individual direction indicators | 10 |
| 4 | Stop lamp | 9 |
| 5 | Side repeaters | 9 |
| 6 | Ball joint dust cover | 8 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Brakes | 22.1% | 95 |
| 2 | Suspension | 19.8% | 85 |
| 3 | Emissions & environmental | 17.2% | 74 |
| 4 | Tyres | 16.1% | 69 |
| 5 | Steering | 9.1% | 39 |
| 6 | Body, structure & corrosion | 6.3% | 27 |
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 | 35 | 11.4% |
| 30-60k | 70 | 8.6% |
| 60-90k | 129 | 10.1% |
| 90-120k | 109 | 15.6% |
| 120-150k | 73 | 20.5% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 98 | 11.2% |
| 2022 | 108 | 16.7% |
| 2023 | 80 | 10.0% |
| 2024 | 72 | 16.7% |
| 2025 | 72 | 15.3% |
What to check before buying a 1990 Sl
The failure pattern for this year is specific enough to inspect against: lighting & signalling accounted for 9.1% of tests. Start there.
- Lighting & signalling (9.1% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Suspension (4.2% 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.
- Brakes (4.0% 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.
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 1990 Mercedes-Benz Sls pass their MOT?
86.1% of the 430 1990 Mercedes-Benz Sl MOT tests in this dataset passed — a 14.0% fail rate.
What is the most common MOT failure on a 1990 Mercedes-Benz Sl?
Lighting & signalling, recorded in 9.1% of tests, followed by suspension (4.2%).
Does the 1990 Sl get worse with mileage?
Its MOT fail rate rises from 11.4% in the 0-30k band to 20.5% in the 120-150k band.
Methodology & source. Based on 430 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.