Modern vehicles tend to give warnings whenever something goes wrong. In most cases, this comes in the form of a check engine light triggered by the OBD-II system. Unfortunately, your car can only alert you to problems the computer can detect, which means that your vehicle is blind to specific issues that its sensors can't see.

When it comes to your exhaust system, the last stop for the computer is an oxygen sensor located behind the catalytic converter. Anything that happens downstream from this sensor is essentially invisible to the onboard diagnostic system, including your muffler. However, these three signs can alert you to muffler trouble, even if your car's computer can't.

1. Your Exhaust Sounds Unusually Loud

A leak anywhere in your exhaust system can create thunderous exhaust noise. Your muffler helps to keep your exhaust's noise levels tolerable, but it's also the final part of the exhaust system. As a result, a leak anywhere in your exhaust system can bypass the muffler and create a loud racket. However, there are a few ways you can narrow the trouble down to the muffler and not another component.

First, try to determine if you still hear your exhaust primarily from the rear of your car.  Leaks upstream from the muffler can make your exhaust rumble directly below the passenger cabin or the engine. You can try listening from outside your vehicle while it's running, but don't get too close to your car's tailpipe or any other part of the exhaust system.

2. You Hear a Rattling Noise

Your exhaust system runs the length of your vehicle. Since most exhaust components are relatively heavy, they need various hangers and brackets to keep them in place. These items can wear out on older cars, usually rusting due to salt and water exposure. When this happens, parts of the exhaust system can come loose.

Loose mufflers are a common ailment on many cars as they age. If a hanger or clamp fails, the muffler can rattle and bang against the underside of the car. Although this might seem like a minor problem, it's a good idea to repair it as soon as possible. If left alone, a loose muffler can damage your vehicle or even break free of the rest of the exhaust system.

3. There Are Obvious Signs of Rust

You can use your eyes as well as your ears to detect problems with your muffler. Many exhaust leaks form due to rust on exhaust components, including the muffler. While surface rust isn't necessarily an issue, penetrating rust is a problem. Periodically check your muffler for signs of rust. If you can see metal flaking away or holes developing, then your car will require a muffler repair sooner rather than later.