Exhaust System and Emissions

1. Exhaust System

The exhaust system must be complete, secure, silence effectively and be without serious leaks.

Before the test, check the exhaust system by starting the engine and then listening to the exhaust from the rear of the vehicle. Listen out for any excessive noise that could indicate a leaking exhaust joint; anything too loud may indicate a split pipe or muffler box. You should also check along the system's length that there are no obvious leaks; you can test this further by briefly blocking the open end of the exhaust pipe with a balled up rag to show up any small leaks that may appear as the gas pressure builds up.

2. Exhaust Emissions

The vehicle must meet the requirement for exhaust emission depending on its age and fuel type.

Although the actual emission test requires specialist equipment, you can perform a basic check by looking for any signs of smoke leaving the exhaust when engine is idling. Follow this by revving this engine at around 3000 rpm, watching for any puffs of smoke as the throttle is released.

Exhaust smoke could mean the carburettor needs to be adjusted or replaced, or that the fuel injection system requires expert attention - this is particularly likely with diesel engines. Blue smoke may indicate that engine oil is burning in the cylinders, whilst black smoke means too much petrol is being burnt. Clouds of dark grey smoke may point to an out-of-tune diesel engine.

Click here to read more from InterCars.co.uk