Symptoms Of A Bad Muffler – Warnings of Exhaust System Failure

For a vehicle to run smoothly, all its components should work properly. The best way to ensure this is by carrying out proper and regular scheduled maintenance.

This includes rendering tender loving care [TLC] to the exhaust systems. The exhaust system is in its well-working state when it is neither heard nor seen.

Failing or a bad exhaust system will affect the overall performance of a vehicle. It’ll lead to high fuel consumption and change the tone or sound of the car.

This article will explain the symptoms of a bad muffler in a vehicle. It’ll also answer some related questions about the subject. Grab a seat and let’s dive right in.

Symptoms Of A Bad Muffler

Regardless of the cause of a bad muffler, a broken exhaust muffler will project a few common symptoms to notify the driver of the underlying issues in the exhaust system. Contact an ASE-certified mechanic to rectify the issues. We’ve outlined the symptoms of bad mufflers in the following few paragraphs.

Symptoms Of A Bad Muffler

Annoying exhaust noise

One of the exhaust leak symptoms is a loud exhaust noise. This commonly happens to the exhaust mufflers as opposed to other exhaust components that are closer to the engine.

Auto manufacturers designed exhaust systems to expel waste exhaust gas out of the vehicle. As the waste gas flows through the exhaust systems, it also passes through the muffler.

An exhaust muffler comprises chambers and partitions that help to reduce vibrations produced during a combustion cycle. If the muffler fails, it causes pre-muffled waste gas to leak, increasing the exhaust sound.

However, not that exhaust leaks only occur on the muffler, it can also occur on other exhaust components. But in most cases, loud exhaust noise is traceable to a leak on the muffler itself. Wherever the aggressive noise is coming from, a certified technician will have to troubleshoot and fix it.

Engine misfiring

Modern engines are finely tuned machines where all components must work in harmony for them to work effectively and efficiently.

One of the harmonic systems is the exhaust system which begins at the exhaust valves inside the head cylinder, which allows gas passage through the exhaust headers into the exhaust pipes, then to the catalytic converter, and to the exhaust muffler, which reduces the noise and expels the gas through the exhaust tailpipe.

If any of these components fail or deteriorate, it’ll affect the overall vehicle performance, including poor acceleration and engine misfiring. If you’re wondering, ‘can a bad muffler cause rough idle?’ A straight-to-the-point answer is yes. Engine misfiring is likened to rough idle.

If there’s a hole in the muffler and it loses its efficiency, it will lead to engine misfiring and stalling, especially when decelerating.

Knocking or banging sound under the vehicle

If you hear banging or knocking sounds under the vehicle, especially when driving, check the exhaust mounts. It could be you have loose exhaust mounts or broken exhaust pipes.

Check under the vehicle and see what’s happening underneath. If you discover a loose exhaust mount or broken exhaust pipes dragging on the road, fix the cause as soon as possible. You shouldn’t be driving like this.

A burning smell Emitting from under the hood

The exhaust manifold is attached to the cylinder head. Between these components is the manifold gasket, also known as an exhaust gasket. If there’s a tear or leak from this component near any plastic or wiring harness, the expelling heat from the exhaust will cause these components to burn.

If this happens, you’ll perceive a smell like burning rubber. You may also see smoke emitting from these areas. Don’t wait until you see smoke before looking for a solution. Track the culprit or seek professional help when you notice a rubber burning smell from the engine bay.

Poor acceleration

If you have to push down the accelerator pedal further than usual before the vehicle responds, especially from a standing point, check the exhaust system. This shows the exhaust system is not working as it should. 

This is often a result of a leak somewhere in the exhaust system. Usually, the leak is too small to produce an aggressive noise. However, it is important to note that several other factors can cause poor acceleration.

Bad gas mileage

A less noticeable sign of a failing exhaust system is high fuel consumption. You’ll agree that several factors can cause bad gas mileage, and one of these factors is an underperforming exhaust system.

Now, you may wonder, why will an underperforming exhaust system cause bad fuel economy? The reason is, when an exhaust system is underperforming, the engine will compensate by working harder, causing it to burn more gas.

Condensation from the exhaust pipes

Mufflers and exhaust pipes are prone to condensation through moisture due to heat buildup in the exhaust system. Moisture is created in the exhaust system during normal engine operation. This moisture sits in the exhaust pipe and gradually eats the exhaust pipe and the layer of the exhaust muffler.

Over time, as the exhaust system passes several warm-up and cool-down cycles, the seams of the muffler and the exhaust pipes wear off and start leaking out exhaust gas. You may also notice a strange noise from the exhaust, which increases with time.

If you notice excessive condensation from the exhaust pipes, it could be the exhaust pipes and the muffler is wearing off.

muffler issues

What problems can a Bad Muffler Cause?

A muffler, as an integral part of an exhaust system, serves two main purposes – to muffle exhaust gas out of the engine and to reduce loud exhaust noise. What happens if the muffler fails?

A failed or broken exhaust muffler will cause a series of problems with the overall functionality of a vehicle. A muffler comprises chambers and partitions that help reduce exhaust noise. If any issues exist in these chambers, it’ll cause loud noise from the exhaust.

A faulty exhaust muffler will cause pre-muffled byproducts to leak, causing rattling, thumbing, and clunking noise from the exhaust. It’ll cause other problems like poor fuel economy, poor acceleration, engine misfiring, and rust condensation on the exhaust pipes.


What does a muffler going bad sound like?

There is no doubt that the most common sign of a bad muffler is a loud sound. What does a bad muffler sound like, anyway? A compromised muffler will produce a thumping or clunking sound underneath a vehicle.

Some exhaust mufflers have baffles to silence exhaust noise. The baffles may become loose or break and cause a rattling noise.

What happens if you drive with a bad muffler?

Driving with a bad muffler is dangerous. Muffler issues is not something you should disregard and fix at your own pace. Once you suspect any sign of a bad muffler, stop the vehicle and inspect it and the entire exhaust system to see if there is any visible rust or hole on it.

Even if you don’t see any rust or leak, contact a professional mechanic to do a thorough diagnostics. The leak in your exhaust system can cause carbon monoxide to get into your vehicle’s cabin.

If you continue driving in this state, you’ll be inhaling dangerous exhaust fumes. This will cause you to feel nauseous, dizzy, have headaches, and in any severe case, you may lose consciousness.

Can a bad muffler cause a check engine light?

An exhaust leak of any kind, either as a result of a bad muffler or rust, will trigger a check engine light. Why is it so? This is simply because an exhaust leak will trigger a false or poor reading on the O2 sensor.

Do not conclude you have a compromised exhaust muffler because of a check engine light on the instrument cluster. Several factors can cause the powertrain control module [PCM] to trigger it.

What is the average cost to replace a muffler?

The amount of replacing a muffler depends on several factors, like location, car makes, and model. In any case, the estimated cost of replacing a muffler is between $810 to $870. The replacement parts should cost $760 to $780, whereas labor should be around $50 to $90.

This is just an estimated rate. The exact rate can be higher or lower depending on your car and location.

Final words

Mufflers play a critical role in the exhaust system and that’s why they can cause performance issues when it starts failing.

At this juncture, you have learned the symptoms of a bad muffler and its effect. Whenever you notice any of the outlined symptoms, inspect the muffler for leaks and rust. You can take your vehicle to an ASE-certified mechanic to track the cause and fix it.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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