Mercedes-Benz SLK MOT pass rate & common failures
The Mercedes-Benz SLK appears in 354,328 MOT tests spanning model years 1991–2023, and 80.5% of them passed. Coupes & convertibles of a similar age fail at 18.9%, so the SLK sits squarely on the average. Its most common failure areas are suspension, lighting & signalling and tyres.
Best and worst SLK years
Ranked across SLK years with at least 1,000 tests. Older cars fail more simply because they are older — compare years close together in age before drawing conclusions.
What the MOT record shows
Build year matters more than the headline suggests: 2016 cars pass 88.7% of the time while 2004 cars manage 75.8%, a 12.9-point spread.
No single area dominates — suspension (9.1%) and lighting & signalling (7.0%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are coil spring, headlamp aim and ball joint — coil spring alone was recorded 16,798 times.
Mileage is the strongest signal on the record: 8.6% of 0-30k cars fail, rising to 28.7% once past 150k — 3.3× the risk.
The diesel cars hold up better: 16.5% fail against 20.3% for petrol, a 3.8-point gap across 354,317 tests.
Brakes is the most common advisory, noted on 24.6% of tests — work that passed today but is likely due soon.
The trend is worsening — 18.5% of tests failed in 2021 against 20.3% in 2025, the usual pattern as a fleet ages.
How it compares
By model year
Every SLK model year with a usable sample. Years with their own detailed report are linked.
| Year | Tests | Pass rate | Fail rate | Most common failure |
|---|---|---|---|---|
| 1996 | 272 | 79.0% | 21.0% | Lighting & signalling |
| 1997 | 4,630 | 80.0% | 20.0% | Lighting & signalling |
| 1998 | 7,208 | 79.1% | 20.9% | Lighting & signalling |
| 1999 | 9,521 | 79.9% | 20.1% | Lighting & signalling |
| 2000 | 12,123 | 80.1% | 19.9% | Lighting & signalling |
| 2001 | 14,091 | 80.2% | 19.8% | Lighting & signalling |
| 2002 | 12,257 | 81.0% | 19.0% | Lighting & signalling |
| 2003 | 11,475 | 78.6% | 21.4% | Lighting & signalling |
| 2004 | 19,843 | 75.8% | 24.2% | Suspension |
| 2005 | 30,137 | 76.7% | 23.3% | Suspension |
| 2006 | 23,127 | 76.9% | 23.1% | Suspension |
| 2007 | 22,136 | 77.3% | 22.8% | Suspension |
| 2008 | 20,039 | 77.7% | 22.3% | Suspension |
| 2009 | 15,586 | 78.3% | 21.7% | Suspension |
| 2010 | 12,840 | 79.3% | 20.7% | Suspension |
| 2011 | 15,074 | 82.9% | 17.1% | Suspension |
| 2012 | 33,408 | 82.3% | 17.7% | Suspension |
| 2013 | 27,434 | 82.7% | 17.3% | Suspension |
| 2014 | 28,281 | 85.2% | 14.8% | Tyres |
| 2015 | 27,715 | 87.1% | 12.9% | Tyres |
| 2016 | 7,027 | 88.7% | 11.3% | Tyres |
Most common failures (all years)
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Suspension | 9.1% | 32,389 |
| 2 | Lighting & signalling | 7.0% | 24,905 |
| 3 | Tyres | 5.1% | 18,094 |
| 4 | Brakes | 5.1% | 17,916 |
| 5 | Visibility | 2.6% | 9,382 |
| 6 | Emissions & environmental | 2.1% | 7,255 |
| 7 | Body, structure & corrosion | 1.2% | 4,253 |
| 8 | Seat belts & restraints | 1.1% | 3,714 |
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 | 16,798 |
| 2 | Headlamp aim | 11,330 |
| 3 | Ball joint | 9,428 |
| 4 | Tread depth | 9,030 |
| 5 | Rigid brake pipes | 8,748 |
| 6 | Headlamp | 6,924 |
| 7 | Washers | 5,393 |
| 8 | Wipers | 5,328 |
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 | 24.6% | 87,180 |
| 2 | Tyres | 23.8% | 84,401 |
| 3 | Suspension | 18.7% | 66,348 |
| 4 | Lighting & signalling | 6.5% | 23,089 |
| 5 | Other defects | 6.0% | 21,416 |
| 6 | Body, structure & corrosion | 4.9% | 17,300 |
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 | 31,975 | 8.6% |
| 30-60k | 120,217 | 15.5% |
| 60-90k | 115,726 | 21.6% |
| 90-120k | 60,736 | 25.4% |
| 120-150k | 19,654 | 27.2% |
| 150k+ | 5,824 | 28.7% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Petrol | 274,795 | 20.3% |
| Diesel | 79,522 | 16.5% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 75,766 | 18.5% |
| 2022 | 73,350 | 18.7% |
| 2023 | 71,483 | 19.6% |
| 2024 | 68,344 | 20.3% |
| 2025 | 65,385 | 20.3% |
What to check before buying a Mercedes-Benz SLK
- Suspension (9.1% 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.
- Lighting & signalling (7.0% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Tyres (5.1% 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.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
What is the MOT pass rate for the Mercedes-Benz SLK?
80.5% of the 354,328 Mercedes-Benz SLK MOT tests in this dataset passed, a 19.4% fail rate, across model years 1991–2023.
What does the Mercedes-Benz SLK most often fail its MOT on?
Suspension, recorded in 9.1% of tests, then lighting & signalling (7.0%).
Which SLK years are best and worst for MOT results?
2016 has the best pass rate at 88.7% and 2004 the weakest at 75.8%, from 7,027 and 19,843 tests respectively.
How much does mileage affect SLK MOT results?
Fail rates run at 8.6% for cars in the 0-30k band and 28.7% for 150k+, a 20.1-point difference.
Is the diesel or petrol SLK more reliable at MOT time?
On MOT-testable defects the diesel fails 16.5% of the time against 20.3% for the petrol. This covers testable items only, not engine or gearbox reliability.
Methodology & source. Based on 354,328 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.