How do you know if you need a new exhaust What are the effects of having an old exhaust?

If the car starts sounding louder than normal, or if the exhaust note changes (essentially, if it starts sounding like a race car and it never did before), crawl under and look for leaks, holes, etc. There are two effects of having a bad exhaust. One is just bad--it can upset the way the car runs, and possibly cause it to stop running after a while. The other's terrible--exhaust gases can find their way into the ventilation system, get into your car and kill everyone inside.