How to Find Exhaust Leaks

So you think you got an exhaust leak? Maybe your car is making that clicky pfft-pfft-pfft sound that gets more rapid the faster you go. Maybe your car is as loud as a school bus. Or maybe you’re getting fumigated by exhaust while you drive (not good, btw). Whatever it is, you gotta get your exhaust system fixed. In this article, you’ll learn how to find exhaust leaks and what you need to do to fix them.

What is an Exhaust System?

First things first…. What the hell does your exhaust system do? 

I’m gonna keep this simple… your exhaust system is basically a system of parts and metal pipes that transports exhaust from your engine to the back of your car. Your exhaust system does three things:

  1. Helps your engine breathe
  2. Keeps your car quiet
  3. Minimizes pollution

Let’s talk a bit more about these three things, shall we?

Helps your engine breathe

In case you didn’t know, your car’s engine breathes. 

It takes in fresh air in the front to feed the tiny explosions (fire needs air) that happen inside your engine (internal combustion).


After said tiny explosions happen, they (like all explosions) give off a byproduct/smoke known as exhaust. This exhaust is passed out of the engine, sent through the exhaust system, and is released at the back of your car to pollute the air you and I breathe. Yay!

Keeps your car quiet

Remember what I said about all those tiny explosions going off inside your engine? Well, they make a lot of noise. And the faster you go, the more explosions there are, and the more noise there is!

Your exhaust system is an outlet of sorts for this sound and energy, and therefore makes a lot of noise. To help minimize said noise, your exhaust system contains a muffler. 

For those of you who can’t put 2 and 2 together, it’s called a muffler because it muffles sound (duh).

Minimizes Pollution

We’ve touched on the fact that exhaust isn’t good to breathe in. It’s toxic and can actually kill you if you breathe in enough of it. Scary, right?

To help reduce levels of toxicity, your exhaust system contains a filter known as a catalytic converter. It uses precious metals like palladium and platinum to change the chemical composition of your car’s exhaust, making it less harmful to the environment.

Exhaust System Parts

To better understand how to find exhaust leaks, it is helpful to know about the parts that make up an exhaust system.

Your exhaust system isn’t a single continuous pipe. 

It starts with the exhaust manifold, which is the part bolted to the engine that captures the exhaust and funnels it to the pipe system.

The exhaust manifold channels exhaust into a pipe that typically leads to the catalytic converter. This is often a flex pipe that is covered in a metal mesh. Given that this pipe flexes, it is more susceptible to wear and tear…. And you guessed it – exhaust leaks.

From the catalytic converter, there is another pipe that leads to the muffler.

And the final pipe in the system is your tail pipe, which comes off the muffler and is the pipe at the rear of your car that spews exhaust into the air.

The exhaust system on your specific car may be a little different than what I just described. You may have multiple pipes. Or you might have resonators along the pipe system. These act like additional mufflers to keep your car quiet.

Here’s a diagram of a typical exhaust system from Walker Exhaust – one of the leading producers of replacement exhaust system parts. Check out this page for a closer look at each part of an exhaust system.

exhaust system diagram
Diagram courtesy of Walker

It’s important to know about all of these individual pieces because an exhaust leak can occur at the spots where each part is bolted together. Joints or bolts can wear out. And connections often use gaskets which, you guessed it, can wear out and cause a leak in the system.

What is an exhaust leak?

An exhaust leak is a hole in your exhaust system. 

Why do exhaust leaks happen?

Exhaust leaks generally happen because of age. Metal gets weak, rust happens, and cracks, holes, etc. form.

Your exhaust system is on the underside of your car so it takes all kinds of abuse. It is constantly exposed to weather, road debris, and your crappy driving habits when you bottom out driving over curbs.

Something else to keep in mind is that your exhaust system gets super hot! After running for a while, it can reach several hundred degrees Fahrenheit.

Exhaust systems are designed to be durable. But they do take a beating and metal pipes eventually rust and start to break down.

Exhaust leak symptoms

How do you know you have an exhaust leak? There are a few exhaust leak symptoms that are good indicators you have a leak. It could be a sound, a smell, or a warning light.

Exhaust leak sound

If you have an exhaust leak, the most common of exhaust leak symptoms is a loud sound. The sound can be different depending on how big the leak is and where it is on the system.

If your exhaust leak is before the muffler, it could be loud AF. Your car might start to sound like a school bus. You might think it’s cool. But it’s not. Just ask your neighbor.

If your exhaust leak is up closer to the engine… maybe in your exhaust manifold… it will make a ticking sound. Or a sound that goes pfft-pfft-pfft-pfft. The sound will get more rapid the faster you go.

If you’re hearing the ticking/pfft-ing sound, there’s a good chance it will go away after driving for a while. This is because this sound is generally caused by a crack on your exhaust manifold. As the exhaust manifold heats up, the metal expands and the crack gets smaller and can even seal.

Exhaust smell in car

An exhaust leak can cause an exhaust smell in your car.

If this happens, you should get the leak fixed asap. Breathing in exhaust fumes is extremely dangerous… so don’t mess around here.

The reason you’re getting an exhaust leak smell in your car is likely because the leak is under the passenger compartment and harmful exhaust fumes are flowing straight up into your car.

Don’t mess around here. Get this one fixed.

Check engine light


Depending on where your leak is, you might get a check engine light on your dashboard. 

This generally happens when an exhaust leak occurs near an oxygen sensor. 

Many exhaust systems have oxygen sensors that monitor the chemical makeup of your exhaust and send the data to your car’s computer.

Leaks near these sensors mess up the flow of exhaust, and trigger the sensor to send an alert to your car’s on-board computer that something is wrong.

How to find exhaust leaks

Let’s talk about how to find exhaust leaks.

You’re going to have to examine the underside of your car. So having access to a lift will be helpful. 

If you don’t have a lift, you can get your car on jack stands or up on ramps. Please use all safety precautions if you are doing this! You need to be certain your car is secure before getting under it!

You may visually be able to see an exhaust leak. A leak often has black soot around it.

You also might be able to feel it if you run your hand around the pipes while the car is running. Just be careful not to burn your hand on hot exhaust pipes if the car has been running for a while!

If none of this works, here’s the not-so-big secret on how to find exhaust leaks…. plug your tail pipe with a rag and then listen to your exhaust system.

Plugging the tailpipe blocks your exhaust system’s main outlet. Now all your exhaust is going to try to escape through the leak opening. The greater pressure coming through the exhaust leak will be noisy.

It may be helpful if a friend helps you do this. Your friend can hold the rag on the tailpipe while listen along the whole system and pinpoint the leak.

Exhaust repair

Now that you’ve found the leak, it’s time for an exhaust repair job.

Patching your exhaust with products like JB Weld’s Exhaustweld or the good ole soup can patch will work for a little while. 

These solutions seem like good ideas on paper, but they are band-aid solutions. They won’t last very long.

The best thing to do is replace the section of pipe with the leak in it.

Alternatively, if you’re a welder or know of a good local welding shop, it might be cheaper to have a new piece welded in. 

Exhaust manifold leak

If it turns out you have an exhaust manifold leak (which is a common problem) you’re going to have to replace your exhaust manifold.

As mentioned earlier, hearing that ticking or pfft-pfft-pfft sound is likely an exhaust manifold leak.

This is generally a pretty easy repair. But depending on your car, accessing the exhaust manifold might be a challenge.

Do I need to fix an exhaust leak?

You may be wondering if you even need to fix an exhaust leak.

Can your car continue to run with the leak?


Yes.

Should you continue to run your car with an exhaust leak?

Probably not.

It comes down safety. There’s a reason car tail pipes are at the very rear of your car… exhaust is toxic!


And if you have a leak that is letting exhaust into your passenger compartment, you and your passengers don’t want to be breathing that stuff in. 

Plus, if your car sounds like a school bus, I’m sure you’re probably pissing off your neighbors. So just get it done!

Conclusion

The best way to find an exhaust leak is to block off the tail pipe with a rag. This will stop the flow of exhaust and put more pressure on the exhaust leak. Once you find the spot, you can either replace the part – be it a pipe or your exhaust manifold. Or you can possibly have a new piece welded in. Good luck!


About the Author

Kevin

Hi I’m Kevin and I’m a car guy. I first got the bug as a kid when I helped my dad rebuild the motor in his 1969 Mustang. I shadowed him for countless hours doing all kinds of hands-on work in the garage. As I got older, I started working on my own cars – from new transmissions to stereos to fine detailing. I started this website to share some of the things I’ve learned over the years.

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