Got a weird CLUNK! coming from underneath your vehicle? How about a strong stench of rotten eggs permeating your interior?

Or maybe your car, truck, or SUV simply isn’t running right…

…Well friend, those are all indicators that your exhaust system may be going bad.

We said “may” up there, simply because some of the issues we’ll discuss here could very well be caused (or at least, exacerbated) by other problems with your vehicle. So you should always take a holistic view of automotive troubleshooting and look at other areas (suspension, brakes, etc.) that may be causing the clunks and rattles you’re hearing.

That way you’ll know for sure before plunking down your hard-earned cash on a new exhaust system.

side by side comparison of two exhuast systems & mufflers
Rust and normal use take a heavy toll on your exhaust system, so don’t be surprised if you discover exhaust-related issues—even on a vehicle that’s only a few years old. (Image/Steve Baur)

Common Causes of Automotive Exhaust Problems

Your vehicle’s exhaust system takes a lot of abuse, from intense hot/cold heat cycles, to the jolts and vibration from potholes and uneven roads.

Oh, and let’s not forget the constant threat of rust. In fact, rust is often the main culprit behind a lot of these issues, so if you live in an area that sees a lot of rain or snow (or SALT!), then don’t be surprised if your exhaust system looks worse than one on a similar vehicle that lives down south.

That’s because rust attacks your exhaust system from both outside and in. It’s normal for moisture to build up in an exhaust system overnight—hence the steam that comes out for a few minutes during your morning commute. And if you don’t drive often or only take short trips, the exhaust system doesn’t get warm enough to burn off that moisture. As a result, it will start eating away at your pipes from the inside.

Symptoms & Signs of a Bad Automotive Exhaust System

The good news is—and you’ve probably discovered this already—a failing exhaust system Doesn’t Go Gentle Into the Good Night. Nope, it’ll likely give you a heap of warning signs that trouble’s afoot, like-a so:

  • Excessive movement (grab the tailpipe & wiggle it!)
  • Cracked welds at joints (strong exhaust smell outside)
  • Cracks in the exhaust manifold(s) (pops & pinging noises)
  • Split or open seams, especially on mufflers (LOUD!)
  • Pinholes or punctures in tubing or muffler(s) (also LOUD)
  • Loose heat shields (annoying rattles)
  • Loose or broken clamps and brackets (clunks & clangs)
  • Missing bolts, clamps, or other parts (rattles & movement)
  • Dents or other damage from road debris, hitting a curb, etc. (visible scars/dents)
  • Check engine light

How to Spot a Bad Catalytic Converter

side by side catalytic converter comparison
New factory-fit catalytic converters are readily available now, and will keep your vehicle emissions compliant if you face regular smog testing in your region. (Image/Christopher Campbell)

As part of your vehicle’s exhaust system AND emissions control system, the catalytic converter deserves its own special section here. Nowadays a good catalytic converter can easily last several years, but there are a myriad of factors like driving environment, fuel quality, and driving style that could impact a catalytic converter’s lifespan.

Here are a few indicators that your catalytic converter has failed:

  • Strong rotten eggs stench
  • Sluggish engine performance, especially on acceleration
  • Check engine light on the dash
  • Poor fuel economy
  • Glowing red hot catalytic converter (look underneath your car after a drive!)

Don’t be tempted to simply remove your catalytic converter here either. Since they are mandated by the government, there’s a good chance that it’s illegal to tamper with, modify, or remove your catalytic converter where you live. Besides, modern catalytic converters don’t cost you horsepower nowadays, so there’s really no reason to remove it in the first place.

Since it’s such an important topic, we’ve got a much more in-depth article on spotting issues with your catalytic converter. Check it out here: How to Diagnose Catalytic Converter Problems

stock exhaust manifold for a b15 2004 nissan sentra
Many modern engines use a “Pre-Cat” catalytic converter built into the exhaust manifold, if your main converter looks fine under the car, you might want to investigate the “kitten” located upstream. (Image/OnAllCylinders)

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Exhaust systems are far more than just a jumble of pipes under your vehicle. Picking the best exhaust system for your specific application can be a complex, nuanced process. The good news is, if you know what your expectations are, then picking the right aftermarket exhaust becomes really easy.

To help you out, we’ve got oodles (yes, oodles) of articles and tech stories on exhaust systems. If you’re in the market for an exhaust system upgrade, here are some good articles to check out: