Exhaust leak at the MOT: which cars fail on it most
2.6% of failed initial MOT tests in 2025 recorded this defect: 234,303 of 9,185,328. By age, it was most common on vehicles 20 years old and over (4.9%) and least common on vehicles 3 to 5 years old (0.1%).
It is one of the 10 most common MOT failures on 23 of the 332 car models we cover. Against vehicles of the same age, it was most common on the Smart Forfour, the Peugeot Horizon and the Fiat Punto. On the Smart Forfour, 5.7% of failed tests had it, against 1.3% for all vehicles of the same age.
The DVSA records it as “Exhaust has a major leak of exhaust gases”. A failed test can have several defects.
What the MOT checks
A major leak of exhaust gas from the exhaust system.
The MOT inspection manual lists “Exhaust system has a major leak or is insecure” as a major defect, so the vehicle fails.
Car models where it is most common
| # | Car | Share of failed tests | Against same age |
|---|---|---|---|
| 1 | Smart Forfour5,678 failed tests | 5.7%324 tests | 4.3×all: 1.3% |
| 2 | Peugeot Horizon1,964 failed tests | 5.6%110 tests | 3.7×all: 1.5% |
| 3 | Fiat Punto20,760 failed tests | 10.1%2,094 tests | 3.0×all: 3.4% |
| 4 | Peugeot 20864,789 failed tests | 5.0%3,213 tests | 2.9×all: 1.7% |
| 5 | Fiat Grande Punto3,500 failed tests | 10.6%370 tests | 2.8×all: 3.8% |
| 6 | Volkswagen Fox11,461 failed tests | 10.6%1,214 tests | 2.7×all: 3.9% |
| 7 | Alfa Romeo Mito6,404 failed tests | 7.8%499 tests | 2.6×all: 2.9% |
| 8 | Nissan Juke99,185 failed tests | 4.7%4,680 tests | 2.4×all: 2.0% |
| 9 | Chevrolet Aveo2,837 failed tests | 7.9%224 tests | 2.3×all: 3.4% |
| 10 | Fiat Panda30,213 failed tests | 6.8%2,041 tests | 2.2×all: 3.1% |
| 11 | Ford Ka56,418 failed tests | 6.1%3,458 tests | 2.2×all: 2.8% |
| 12 | Vauxhall Zafira66,828 failed tests | 6.3%4,200 tests | 2.1×all: 3.0% |
| 13 | Vauxhall Astra198,624 failed tests | 6.0%11,874 tests | 2.1×all: 2.9% |
| 14 | Peugeot 10741,526 failed tests | 7.1%2,957 tests | 2.0×all: 3.5% |
| 15 | Toyota Land Cruiser1,909 failed tests | 9.5%181 tests | 2.0×all: 4.6% |
Only models where this defect is one of their 10 most common MOT failures, with at least 50 failed tests, have a figure. So a model that isn't listed can still have it, just less often than its other faults. Vans, pick-ups and taxis are left out, as in our rankings. × is the model's share divided by the share for all vehicles of the same age.
How common it is by car age
- 3 to 5 years, first used 2020 to 20220.1% of failed tests, against 2.6% for all ages755 failed tests
- 6 to 9 years, first used 2016 to 20191.0% of failed tests, against 2.6% for all ages21,553 failed tests
- 10 to 14 years, first used 2011 to 20152.5% of failed tests, against 2.6% for all ages84,216 failed tests
- 15 to 19 years, first used 2006 to 20104.0% of failed tests, against 2.6% for all ages87,452 failed tests
- 20 years and over, first used 1985 to 20054.9% of failed tests, against 2.6% for all ages40,325 failed tests
Not shown, with fewer than 50 failed tests with this defect: vehicles under 3 years old.
All-vehicle figures cover vehicles first used from 1985 to 2024: 9,185,328 of the 9,193,164 failed initial tests in 2025.
How these figures are counted
These are failures recorded at initial MOT tests in 2025. Retests are not counted. A defect found on more than one wheel, lamp or joint at the same test counts once. "Same age" is the defect's share of failed tests for all vehicles first used in the same years, weighted by the model's own failed tests in each year.
An MOT checks safety and emissions on the day of the test. These figures show where a defect was recorded, not why, and not what a repair costs. Figures: DVSA anonymised MOT tests and results, 2025. Contains public sector information licensed under the Open Government Licence v3.0. What the MOT checks: MOT inspection manual: cars and passenger vehicles, GOV.UK, read 1 Nov 2026.
How we choose and rank these defectsOther body, chassis, structure faults
Share of all failed initial MOT tests in 2025.