The silencer is the part of the exhaust that usually needs attention first, as 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 take your car to the nearest Kwik Fit Centre where a Qualified Exhaust Specialist 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.