Exhaust system
The exhaust system will fail the MOT if:
- Part of the system missing or excessively deteriorated
- A mounting is missing or damaged so it does not support the system
- There is a major leak
- The system is excessively noisy (in comparison to a vehicle of the same type with manufacturers fitted system).
Emissions
These are checked using specialised equipment, the specific limits of the check depend on the year that the vehicle was first used on the road. Excessive smoke (checked visually) is a reason for failure.
Please note that, on petrol cars fitted with a catalyst, the emissions may fail if there is a hole in the exhaust due to the tight tollerances on the test machine.
Diesel smoke emissions are checked using a diesel smoke meter.
Fuel system
Any fuel leak will result in a fail. This is checked from under the bonnet and throughout the run of the fuel line from the fuel tank to the engine.
The fuel system will fail if:
- fuel filler cap does not fasten securely
- the seal in the cap is torn, deteriorated or missing
- it has another defect which could/does cause fuel to leak out
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Exhaust, fuel and emissions