2009 Mercedes-Benz Sl — MOT failures & pass rate
Across 2,808 MOT tests, the 2009 Mercedes-Benz Sl recorded an 85.3% pass rate. That is 5.6 percentage points better than coupes & convertibles of a similar age, which fail at 20.3%. Failures cluster in suspension, tyres and lighting & signalling.
What the MOT record shows
No single area dominates — suspension (5.8%) and tyres (5.5%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are coil spring, ball joint and rigid brake pipes — coil spring alone was recorded 98 times.
Mileage is the strongest signal on the record: 5.9% of 0-30k cars fail, rising to 23.5% once past 120-150k — 4.0× the risk.
Brakes is the most common advisory, noted on 21.3% of tests — work that passed today but is likely due soon.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Suspension | 5.8% | 164 |
| 2 | Tyres | 5.5% | 154 |
| 3 | Lighting & signalling | 3.6% | 102 |
| 4 | Brakes | 2.8% | 79 |
| 5 | Visibility | 1.7% | 48 |
| 6 | Emissions & environmental | 1.1% | 30 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Coil spring | 98 |
| 2 | Ball joint | 51 |
| 3 | Rigid brake pipes | 42 |
| 4 | Tread depth | 37 |
| 5 | Headlamp aim | 37 |
| 6 | Individual direction indicators | 36 |
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 | 21.3% | 598 |
| 2 | Tyres | 20.3% | 569 |
| 3 | Suspension | 11.5% | 323 |
| 4 | Other defects | 4.0% | 111 |
| 5 | Lighting & signalling | 3.9% | 108 |
| 6 | Visibility | 3.0% | 85 |
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 | 353 | 5.9% |
| 30-60k | 1,107 | 13.4% |
| 60-90k | 933 | 17.6% |
| 90-120k | 352 | 17.9% |
| 120-150k | 51 | 23.5% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 614 | 14.7% |
| 2022 | 567 | 14.6% |
| 2023 | 565 | 15.2% |
| 2024 | 538 | 14.5% |
| 2025 | 524 | 14.3% |
What to check before buying a 2009 Sl
The failure pattern for this year is specific enough to inspect against: suspension accounted for 5.8% of tests. Start there.
- Suspension (5.8% 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.
- Tyres (5.5% of tests): Usually a quick, known-cost fix, but check tread, age and uneven wear (which can hint at alignment or suspension issues). Typical repair: £50–£120 per tyre.
- Lighting & signalling (3.6% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
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 2009 Mercedes-Benz Sls pass their MOT?
85.3% of the 2,808 2009 Mercedes-Benz Sl MOT tests in this dataset passed — a 14.7% fail rate.
What is the most common MOT failure on a 2009 Mercedes-Benz Sl?
Suspension, recorded in 5.8% of tests, followed by tyres (5.5%).
Does the 2009 Sl get worse with mileage?
Its MOT fail rate rises from 5.9% in the 0-30k band to 23.5% in the 120-150k band.
Methodology & source. Based on 2,808 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.