How to Diagnose an Exhaust Leak
Diagnosing an exhaust leak is one of the easier things you can do for car maintenance, and can make a difference to more than just your car. The fumes usually directed safely away from the car by your exhaust could be leaking into the car's interior - which is very bad news for you and your family.
The good news is that you should be able to detect an exhaust leak at home, and the most important tools are your eyes and ears.
A leaky exhaust system makes a very distinctive sound, particularly when you accelerate. You will notice this as an annoying sputtery sound (kind of like blowing a raspberry) that sounds over the top of your normal engine noise. You might also detect a leak near the exhaust pipe itself if you notice unusual amounts of soot near or on the exhaust pipe on visual inspection of the back of your car.
Once you strongly suspect you have a leak, you can make certain by finding its source. This will also give you an idea of whether you can fix the problem yourself or help you direct the mechanic when you go for repairs.
There are a couple of ways to find the leak. Your mechanic will probably use a tool called a mechanic's stethoscope, which, just as it sounds, is used to listen to specific areas of the engine. These are usually on sale in auto parts stores. While this is possibly the most thorough method to use when looking for a leak, it is difficult if you're not familiar with what the sound of escaping gasses sounds like.
The second method is to put an old damp towel over the exhaust pipe and run your car for a few minutes. After the engine cools down, look carefully over the engine for the telltale smudge of black soot which points to an exhaust leak. A hand mirror taped to a long stick can help you with this, particularly when following the exhaust line underneath the car. (Note: if your engine is spectacularly dirty, like mine usually is, it's worth giving it a clean first using a gunk cleaner from an auto shop.)
Once you're certain of the leak and its source, you have a bit more information to take to your mechanic or use yourself in repairs. After you have the leak fixed, pay special attention to the change in your engine sound, to help you identify leaks in the future.
It is important to keep your eyes and ears tuned for this relatively common problem, as car exhaust fumes can be deadly. Not only do they contain the nortoriously toxic carbon monoxide, car exhaust fumes contain all of the burnt-off remnants of fuel and many other dangerous chemicals. Sadly, quite a few accidental deaths are caused by car exhaust fumes, as courting couples in heated cars have found out only too late.
