You may not become aware of an issue with your exhaust system until you hear a loud sound when driving or even when you take the car in to a garage for an MOT (and there is a problem with the emissions) or service. The exhaust system is made up of a number of different components and sometimes the problem is obvious, other times it may need investigating.
The costs involved with exhaust repair can be just as confusing as a hole in one part of the system can be drastically more expensive than a similarly sized one in a different part of the system.
White smoke coming from the tailpipe is usually a cause for concern. It often indicates that your car could be low on engine coolant from the result of a cracked or warped cylinder head, a cracked engine block or a head gasket failure from overheating. Black smoke coming from the exhaust on the other hand usually indicates that your engine is burning more fuel than it should. This can be because of issues with fuel injectors or air filters or your fuel line made be clogged.
If the exhaust sounds very loud when driving then it usually indicates a hole in the system.