Exhaust leak
How it can appear on an MOT certificate
- “Exhaust has a minor leak of exhaust gases”
- “Exhaust has a major leak of exhaust gases”
What it is
A leak somewhere in the exhaust system, from the engine to the tailpipe, often from a corroded section or a failed joint.
Why it matters
Exhaust gases are harmful, and a leak near the front can let fumes into the cabin. Leaks also make the car noisier and can affect emissions readings.
What to check when viewing a car
Listen for a blowing or ticking noise, especially on a cold start, and look for black soot marks around joints underneath.
Has the car you're looking at had this before?
Free: every MOT, every defect explained in plain English, mileage, tax and ULEZ.
What the MOT categories mean
- Dangerous
- A direct and immediate risk to road safety, or a serious impact on the environment. The car fails and shouldn't be driven until it's repaired.
- Major
- It may affect the car's safety, put other road users at risk or harm the environment. The car fails and should be repaired straight away.
- Minor
- No significant effect on safety or the environment. The car passes, but it should be repaired as soon as possible.
- Advisory
- Something to keep an eye on that could need repairing in future. The car passes.
Related: exhaust and emissions
- Exhaust insecure or mountings damaged
- Emissions over the limit
- Diesel smoke over the limit
- Engine warning light (MIL) on
- Catalytic converter missing or not working
Buying a used car?
General information about this type of MOT defect, not advice about a particular car. How serious it is depends on the car; have any car you're buying inspected by a qualified mechanic.