Blog Car Care Advice 7 Signs of an Exhaust Leak (+ How to Locate the Source)
Car Care Advice

7 Signs of an Exhaust Leak (+ How to Locate the Source)

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Hearing an unusual exhaust noise?

If you also experience abnormal vibrations or reduced fuel efficiency, you might have an exhaust leak that can contain harmful fumes. 

But don’t worry!
We’ll help you confirm the leak and locate its source. We’ll also cover other important aspects, like how to fix it and more.

Let’s go!

This Article Contains:

7 Urgent Signs of an Exhaust Leak You Shouldn’t Ignore

Watch out for these symptoms to catch an exhaust leak early:

1. Strong Gas Smell

If you can smell gas while driving, you probably have exhaust fumes (from a leak before the catalytic converter) slipping into the cabin. You may get a smoky smell if the leak is after the catalytic converter. 

IMPORTANT: If you can smell exhaust in the cabin, roll your windows down and exit the car immediately.

2. Loud Engine Noise

An exhaust leak is typically followed by loud engine noise, including rumbling, hissing, or popping when accelerating.

Note: You may also hear exhaust noise if the muffler isn’t working right. 

3. Unusual Vibrations

Exhaust gas escaping through a damaged flange gasket or exhaust piping can lead to vibrations in the steering wheel or gas pedal.

4. Acceleration and Power Loss

An exhaust leak before the upstream oxygen sensor (O2 sensor) may result in elevated oxygen content readings. This triggers the Engine Control Unit (ECU) to direct more fuel to the combustion chamber. The resulting rich fuel mix then leads to misfires and reduced engine power.

You might face sluggish acceleration despite flooring the gas pedal. 

5. Carbon Buildup

Black spots (carbon particles) typically build up around an exhaust leak, serving as helpful indicators of the leak source. 

6. Lit Check Engine Light

You may see an activated check engine light if the exhaust leak throws off the oxygen sensor readings. This may result in your vehicle running rich or lean.

7. Reduced Fuel Economy

Leaking exhaust gasses could mean more trips to the gas station. This is because an engine running rich and misfiring hurts your vehicle’s fuel economy. 

But what’s causing your exhaust issue?
Let’s find out.

6 Typical Causes of Exhaust Leaks

These are the usual culprits behind leaky exhaust fumes:

  1. Wear and tear due to age can eventually lead to exhaust leaks.
  2. Rusted or corroded exhaust system parts can create openings in an otherwise air-tight system. 
  3. Physical damage from bad road conditions or rough driving can create holes that enable a small leak.
  4. Exhaust manifold gasket wear due to heat and a lack of maintenance will let exhaust fumes escape.
  5. Worn hangers or rubber isolators let engine vibrations damage exhaust system parts.
  6. Poor welding during previous auto repair could let exhaust gasses escape.

Next, let’s pinpoint your exhaust leak.

4 Simple Methods to Locate the Exhaust Leak

Although it’s common to have an exhaust manifold leak, the issue could occur in other exhaust system areas, like before an oxygen sensor or catalytic converter.

Try these methods to spot the source of your leaky exhaust gasses:
Caution: Let the car cool down before you inspect the exhaust system parts.

1. Visually Inspect the Exhaust System

Here’s what to look for:

  1. Check the muffler, resonator, and exhaust manifold for holes or damage. 
  2. Inspect the exhaust port and tailpipe for corrosion or broken hangers. 
  3. Look for black spots on exhaust system parts like the exhaust manifold or exhaust piping. 

2. Block the Exhaust with a Rag

Insert a rag in the exhaust pipe to block the air and start the car. Since the exhaust gases can’t escape from the tailpipe, it will force more exhaust fumes out of the leak, making it easier to locate.

3. Spray Soapy Water

After the car cools, spray soapy water on areas where you suspect the leak. When you turn the car on, the leaky area should foam up, even if it’s a small leak. 

4. Use a Smoke Machine

Send smoke through the exhaust system using a smoke machine. You should be able to notice the smoke coming out of the damaged area.

Now that you’ve found the leak, let’s see what you can do to fix it. 

How to Fix an Exhaust Leak

Many exhaust leak issues require replacements and welding, which must be done perfectly. So, it’s best to leave it to a professional mechanic

However, if it’s a small leak, you can use sealant as a temporary fix. 
Here’s how:

  1. Let the engine cool down.
  2. Clear dust and rust from the surface that’s leaking. 
  3. Smoothen the surface with sandpaper and then wipe it down with some isopropyl alcohol on a towel.
  4. Apply a sealant like muffler putty, exhaust tape, or exhaust band clamp. For putty, let the sealant cure for around 2 to 24 before starting the car again.

You may wonder: Is it fine to ignore the leak?
Read on to find out.

Should You Drive with an Exhaust Leak?

No, it’s best to fix an exhaust leak immediately. The leak can cause car performance issues, which can lead to accidents. It’s also bad for the environment, and you could fail an emissions test. 

But wait, it gets worse!

Exhaust gasses typically contain nitrogen, water vapor, and carbon dioxide, which aren’t toxic. However, if the leak causes incomplete combustion, carbon monoxide could enter your cabin. 

Carbon monoxide is a harmful gas that can be fatal when inhaled in large amounts

Next, let’s resolve some common doubts.

3 FAQs about the Exhaust System and Leaks

Here are answers to questions you may have about exhaust leaks:

1. What Does the Exhaust System Do?

The exhaust system manages these essential functions:

  1. Transport exhaust gasses created during the engine’s combustion process through the system.
  2. Dampen the sounds and vibrations created by the internal combustion process. 
  3. Convert harmful fumes into less harmful gas (like carbon monoxide to carbon dioxide) and dispose of them. 

2. How Much Does it Cost to Fix an Exhaust Leak?

Exhaust repair can cost between $150 to $400, depending on the replacement parts and your mechanic’s labor rate. 

However, you could incur the following costs if you require additional repair:

Note: Exhaust leaks can eventually lead to expensive engine repair. So, it’s best to address any exhaust problem immediately. 

3. Can an Exhaust Leak Cause Engine Failure?

An exhaust issue can throw off your engine’s air-fuel mixture, leading to misfires that may severely damage the engine. Escaping exhaust fumes can also heat up surrounding components and cause engine damage.

Leaving these issues unresolved can lead to engine failure — requiring urgent engine repair. 

Fix Your Exhaust Leak with AutoNation Mobile Service

Exhaust leaks can lead to poor car performance, fuel efficiency, and other dangerous issues. 

That’s why it’s important to have a mechanic inspect your car regularly to catch any exhaust problem early. You could also ask them to inspect the system if you notice any of the signs we covered or while getting an oil change.

Have a leaky exhaust?
AutoNation Mobile Service can fix your vehicle right from your driveway!

We’re a mobile auto repair and maintenance service that can fix any exhaust problem, whether you have a Honda Motor Company or Porsche vehicle. 

Contact us today to resolve any exhaust issue and get a 12-month, 12,000-mile repair warranty.