1999 Mercedes-Benz SLK — MOT failures & pass rate
Across 9,521 MOT tests, the 1999 Mercedes-Benz SLK recorded a 79.9% pass rate. Coupes & convertibles of a similar age fail 22.1% of the time, so this is 2.0pp better than the group it competes with. Failures cluster in lighting & signalling, brakes and visibility.
What the MOT record shows
One area stands out: lighting & signalling, recorded in 15.5% of tests against 6.3% for the next-worst category.
At component level the recurring items are headlamp aim, stop lamp and headlamp — headlamp aim alone was recorded 566 times.
Mileage is the strongest signal on the record: 8.5% of 0-30k cars fail, rising to 32.2% once past 150k — 3.8× the risk.
Brakes is the most common advisory, noted on 32.4% of tests — work that passed today but is likely due soon.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 15.5% | 1,476 |
| 2 | Brakes | 6.3% | 603 |
| 3 | Visibility | 5.8% | 547 |
| 4 | Suspension | 4.5% | 433 |
| 5 | Tyres | 3.5% | 334 |
| 6 | Emissions & environmental | 2.6% | 252 |
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 | 566 |
| 2 | Stop lamp | 509 |
| 3 | Headlamp | 349 |
| 4 | Washers | 333 |
| 5 | Rigid brake pipes | 318 |
| 6 | Wipers | 307 |
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 | 32.4% | 3,087 |
| 2 | Suspension | 26.6% | 2,533 |
| 3 | Tyres | 23.1% | 2,199 |
| 4 | Lighting & signalling | 14.1% | 1,344 |
| 5 | Other defects | 9.9% | 942 |
| 6 | Emissions & environmental | 9.5% | 906 |
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 | 448 | 8.5% |
| 30-60k | 1,556 | 12.8% |
| 60-90k | 2,973 | 19.3% |
| 90-120k | 2,856 | 22.8% |
| 120-150k | 1,230 | 24.9% |
| 150k+ | 456 | 32.2% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 2,344 | 19.8% |
| 2022 | 2,205 | 20.3% |
| 2023 | 1,946 | 21.1% |
| 2024 | 1,631 | 20.4% |
| 2025 | 1,395 | 18.6% |
What to check before buying a 1999 SLK
The failure pattern for this year is specific enough to inspect against: lighting & signalling accounted for 15.5% of tests. Start there.
- Lighting & signalling (15.5% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Brakes (6.3% 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.
- Visibility (5.8% of tests): Wipers, washers, mirrors and screen damage — usually inexpensive, but check for chips in the driver's line of sight. Typical repair: £15–£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 1999 Mercedes-Benz SLKs pass their MOT?
79.9% of the 9,521 1999 Mercedes-Benz SLK MOT tests in this dataset passed — a 20.1% fail rate.
What is the most common MOT failure on a 1999 Mercedes-Benz SLK?
Lighting & signalling, recorded in 15.5% of tests, followed by brakes (6.3%).
Does the 1999 SLK get worse with mileage?
Its MOT fail rate rises from 8.5% in the 0-30k band to 32.2% in the 150k+ band.
Methodology & source. Based on 9,521 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.