What do I need to know about my exhaust?

Exhausts have four main functions: to control noise, to direct exhaust fumes away from passengers, to improve the performance of the engine and to improve fuel consumption.

An exhaust is a series of pipes that links the engine to a silencer and a catalytic converter.

The tailpipe is the part of the exhaust that you can see extending from the back of the car. The silencer joins onto the tailpipe, and then a series of further pipes joins the silencer to the catalytic converter and then the engine.

The silencer contains metal plates or tubes that have a series of holes bored into them. Exhaust gases leave the engine at very high pressures, and the holes in the silencer help to reduce that pressure so that they leave the car more quietly.

Exhausts can corrode from both the inside and outside. How long your exhaust lasts for depends on how far and how often you drive your car rather than the length of time it has been fitted. Vehicles used for short trips around town tend to corrode their exhausts in a much shorter time and distance than cars used predominately for long journeys.

How can I tell if my exhaust needs attention?

The silencer is the part of the exhaust that usually needs attention first. This is because it is the furthest away from the engine and is the most likely to be corroded by acidic moisture. This is because these parts remain relatively cold and give exhaust gases a chance to condense and form pools of corrosive acid inside the system.

You'll know that you have a problem with your silencer because your exhaust starts making a roaring noise.

Other noises to listen out for include hissing, which indicates a crack in the exhaust manifold, exhaust pipe or a leaking gasket. A chugging noise could mean a blockage in the exhaust system.

If you hear rattling under the car it could mean that the exhaust system has become misaligned. And if you can hear a loud metallic vibration, it usually means that something is touching the exhaust pipe or that a clamp, support bracket or mounting is loose. Hangers and brackets hold your exhaust in place. Corroded, fractured or missing hangers or brackets can cause extra stress which can also lead to premature exhaust failure.

Other problems can be identified with a visual check. External rust may not be as serious as it first appears, because it may only be on the surface. But cracks in the pipe or jagged holes around seams and joins between pipes can be signs of bigger problems.

If you hear any strange noises at all coming from your exhaust, the best advice is to bring your car to Hobins' of Preston where a Qualified Technician will be able to help you diagnose the fault.

You then have to make a decision about whether to replace the whole exhaust or just parts of it. Often, if one part is corroded, it is likely that parts of a similar age could be corroded too. Sometimes the different parts of an exhaust fuse together because of heat and they are starting to corrode. That makes separation of the individual parts extremely difficult.

But when they haven't fused together, it's a matter of judgement and consideration based on vehicle usage, driving habits and distances travelled, that will dictate whether individual parts should be replaced or the entire exhaust assembly. Sometimes it can save you time and money to replace more than the corroded part.