Exhaust Leak Sound

Exhaust Leak Sound – Does Your Exhaust Need Replacing?

One of the cheapest (and easiest) ways of bumping up your car’s horsepower or even your car game is exhaust modification. To us, hardcore car lovers, the deep rumble of a V8 is far more appealing than an electric car running 10s in a drag. We all know how melodious the sound of the exhaust can be. Now, imagine the same for an exhaust leak sound.

While some cars may sound like a proper racecar after an exhaust leak, others sound like they’re going through a complete struggle. In this article, we will be covering everything related to an exhaust leak sound, its causes and symptoms, and its replacement cost.

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For the sake of understanding its technicalities on a better level, we will take on a gradual approach. First, we will discuss what an exhaust (manifold) actually is, and how an exhaust system works. And then, we will focus on other important aspects of this article like the symptoms and their replacement (costs).

For those looking to read specific headings, you can always check the table of contents and jump to your desired heading.

What Is An Exhaust Manifold

Exhaust manifolds are a series of pipes and chambers channeling the internal combustion by-products from the combustion chamber. In simple terms, this is how an engine breathes out. It collects gases created from the internal combustion engine and excretes them through an exhaust. Depending on the engine’s cylindrical volume of your car, the number of exhaust manifolds (pipes) may differ.

So, a four-cylinder engine would have four pipes running from each cylinder. Likewise, an eight-cylinder engine, or a V8 engine, would have eight stainless steel or cast-iron pipes running from each cylinder.

These individual pipes join together and form a single tube in different formats as we will read later. This tube runs through several other components – like catalytic converters – to then finally release the gases from its tailpipes. Let’s dive deeper and see how exactly an exhaust system works.

Exhaust Manifold Function

Most of us know that the air an engine sucks is not of the same quality as it breathes out. The air compresses and mixes with fuel for the combustion process during a typical 4-stroke cycle. All this mixing and burning of fuel creates (harmful) oxygen gases. Think of this manifold as a respiratory system. What it breathes in, it lets out.

As we read earlier, in a typical four-cylinder engine, the exhaust manifold is made up of 4 pipes that join together to form a single-unit pipe. Each of these chambers – or runners – bolt onto each of the cylinder heads with the help of an exhaust gasket.

These exhaust gaskets prevent the harmful gases to escape from the manifold-cylinder connection. Instead, they ensure these gases reach the catalytic converters for filtering. Now is when an exhaust manifold steps in.

The individual tubes come together to become a single unit with the help of a cross that welds all of these tubes together. Some tubes – connecting each cylinder – are longer than others. Most engines use such setups as these varying lengths help the engine perform at different RPMs as effectively as possible.

Now, these length variations among tubes help in what is known as the ‘scavenging effect’. In simple terms, it speeds up the process of air intake with the help of a vacuum created from the movement of gas.

Exhaust Leak Sound

The longer (manifold) tubes rush the air outwards to the tailpipes and the shorter tubes help in creating that vacuum. By doing so, they make the intake ready for the next cycle. A perfectly designed exhaust manifold, or ‘Headers’, has a scavenging effect for peak performance at all RPMs.

From thereon, the gases move through the O2 sensor as well as the catalytic converter/ mufflers and resonators.

Headers

A header is an aftermarket exhaust modification that replaces a typical cast-iron exhaust manifold in a vehicle. Considered one of the cheapest ways of increasing your vehicle’s horsepower, these headers can push your vehicle to its limits. An exhaust manifold is enough for your car, but if it wasn’t enough for you, then these headers are your answer.

The sole job of these headers is to improve the flow of gas for the engine for optimum performance at all RPMs. They do so by eliminating the ‘back pressure’ created in a typical engine with a cast exhaust manifold.

In cast-iron exhaust manifolds, the runners – or the manifold tubes – are somewhat shorter than the headers. So, whenever the exhaust valve opens, the flow of gas is relatively restricted because of their short lengths. A header, by using longer runners, eliminates any sort of backpressure and allows the gas to flow (or exit) much more freely.

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As a result, the engine is able to breathe in and out much more smoothly. And as we all know by now, the more air being fed into the engine, the more power it will generate. By doing so, these headers improve the throttle response by a great margin.

Headers Vs. Exhaust Manifolds

It’s not all positive, though. Installing headers comes at a price. Both literally and figuratively. Often, headers are made from stainless steel which is quite labor-intensive. Hence, their costs. The right headers for a vehicle will set you back by $400 – $500. However, before buying headers, question yourself this: is it really worth spending $500 for a 20-horsepower (max) gain?

Likewise, headers are a great way of ruining your fuel economy. Yes, more air is being fed to your engine, but all that air needs to be mixed with fuel for the internal combustion process to take place. So, your cost of increasing performance would be a rise in your fuel consumption.

Also, headers burn more fuel compared to a typical exhaust manifold which can result in more carbon emissions being generated. Apart from a faulty MAP sensor, this can be the reason behind your failing emission tests. Especially in the States.

This is why many cars that most cars that come out of the factory have a cast-iron exhaust manifold installed. They do pretty much the same job, except offer (relatively) less performance, but at a very low cost. Also, exhaust manifolds are better for your fuel economy by a long margin. Headers are only for those who have enough budget and can sacrifice their fuel economy.

What Causes An Exhaust Leak

Before moving on to an exhaust leak sound, we have to first learn what causes it. Because of the unusual position of the exhaust system, they can be subject to a couple of vulnerabilities. Let’s have a quick rundown of some of the causes of an exhaust leak.

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1. Road Impact

The exhaust system is located right underneath the car cabin or the vehicle chassis, which isn’t the most protected place. This leaves the exhaust system in a kind of exposed position to outside matters such as speed bumps. As a result, your car may easily scrape (or hit) against the speed bumps, hence puncturing the exhaust tubes.

Eventually, the exhaust would develop cracks allowing the (gaseous) air to seep out and causing an exhaust leak sound.

2. Corrosion

Most manufacturers opt for cast-iron exhaust manifolds as they are much cheaper than stainless steel. If you have a normal every-driven car, chances are that it’d have a cast iron exhaust manifold. And, as we all know, cast iron is not the strongest of all metals. Coupled with the fact that exhausts generate extreme temperatures, cast iron can rust pretty easily.

As the exhaust catches more and more rust, the cast iron material starts depleting. If you leave the rust unattended (and uncleaned) you’d be looking at several punctures in your exhaust manifold. Eventually, these punctures would develop into an exhaust leak sound like hissing or burbling.

3. Aftermarket Installations And Parts Service

Reasons such as poor fitment or cheaper low-grade aftermarket exhaust systems like headers can damage your exhaust system. Some of these headers are unable to withstand the extreme temperatures in a typical exhaust. Also, their poor fitment can leave certain holes through which the exhaust gas can leak through.

Sometimes, a catalytic converter can become clogged with all the toxic byproducts of the gases passed on from the engine. So, they need to be taken out and cleaned. Although not common, upon reinstalling the converter, you may leave some spaces left open. The connection between the exhaust pipe and the catalytic converter becomes exposed. This can create a path for the exhaust gas to leak through.

Exhaust Leak Symptoms

We read how important a role exhausts can play in the performance aspects of a car. Apart from being a treat for your ears, a (good) exhaust can increase your vehicle’s horsepower as well as throttle response.

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That said, we’ll quickly go through some of the signs that you can look out for an exhaust leak sound. Also, it is better to spot more than two exhaust leak symptoms before you finally conclude that you need a new exhaust.

Exhaust Leak Sound Symptoms #1. Loud Exhaust Noise

As said earlier, some exhaust leaks can make a vehicle sound like a proper racecar. In the case of a broken exhaust system, the sound gets noticeably loud. You can especially hear these sounds upon higher acceleration. This is because you’d often find cracks in broken exhaust pipes. These cracks allow the air to seep through.

In a normal case, the inside pressure waves of an exhaust system travel at the speed of sound. An exposed crack in the (exhaust) system can release the exhaust gas at a much higher pressure. You can hear these sounds in the form of hissing and squeals as you accelerate the car. This makes for one of the easiest ways of identifying an exhaust leak sound when accelerating.

Exhaust Leak Sound Symptoms #2. Unnatural Odor Inside Cabin

An exhaust leak may occur before a muffler or catalytic converter. This means that all of the harmful toxic gases passed on from the engine leave the exhaust system unfiltered. Mostly, these gases enter the vehicle’s cabin in the form of a strong unnatural odor. And you would certainly not want to inhale these engine fumes.

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Not only is this seriously detrimental to your health but these poisonous gases are being released directly into the environment. So, if you are wondering the reason why your cabin smells funny, it’s thanks to an exhaust leak.

Exhaust Leak Sound Symptoms #3. Shakiness And Vibrations

By now we know that an exhaust system is laid right underneath a vehicle’s chassis. so, a crack or a leak in it would certainly cause it to vibrate. This is the result of the gas particles clashing to escape the low-pressure area (outside area) from the high pressure (in the exhaust).

You can especially feel these vibrations at higher acceleration as the exhaust struggles to let out more gas. Mostly, these vibrations are passed on to the vehicle’s gas pedal. So, if you are experiencing vibrations as you floor the car, it is the result of an exhaust leak.

Exhaust Leak Sound Symptoms #4. Worse Gas Mileage

After the individual runners – connected to each cylinder head – meet together to form a single tube, you’d find an O2 sensor. The sole job of this sensor is to determine the amount of unburnt oxygen (or gases) present in the exhaust before it exits the engine.

The data is then sent to the ECU (Engine Control Unit) which has to monitor how rich or lean the engine is running. By doing so, it is able to regulate how much fuel needs to be injected into each cylinder for the internal combustion to take place.

If an exhaust leak seems to occur before this O2 sensor, then the sensor may give off inaccurate readings to the ECU. The ECU would then inject unnecessary fuel causing the engine to run rich. As a result, fuel consumption increases.

So, if you are noticing any variations in your fuel economy whilst also experiencing some of the symptoms described above, your car has an exhaust leak.

Exhaust Manifold Replacement

Say that you have spotted some of the above exhaust leak sound symptoms described above. Plus, you are absolutely sure that your vehicle needs an exhaust manifold replacement. So, what is the next step? Well, that depends on several factors.

First of all, you need to have complete car knowledge. If you have never handled an impact gun before in your life, then you shouldn’t replace an exhaust manifold on your own. In this case, you should leave it to the professionals. In modern vehicles with complicated engines, replacing an exhaust manifold can require some parts of your engine to be disassembled.

With that said, let’s go through some of the steps necessary for an exhaust manifold replacement:

Step 1: Prepping The Vehicle

Jack up your vehicle to the point where you can easily access the manifold from underneath the car. Next, unplug the car’s battery from its source and let the exhaust cool down as it can reach extreme temperatures.

Step 2: Removing Heat Shield And Applying Solvent

Locate the exhaust manifold which can be seen attached to the engine cylinder heads. The next thing on the list is to remove the heat shield protecting the manifold from other engine components. Now that the heat shield is out of the way, you have easy access to the exhaust manifold.

In most cases, it is advised to use a six-point socket for maximum grip because of the bolt’s high temperature. Get yourself a penetrant solvent and spray it on the manifold bolts holding the exhaust gasket and the manifold together. Let the solvent soak for about 15 minutes before continuing on to the next step.

Step 3: Removing (And Installing) Exhaust Manifold

Upon removing all the bolts attaching the cylinder head to the exhaust manifold, the exhaust manifold should come right off. Also, it is important not to apply too much pressure on these bolts. Applying unnecessary force on these bolts will snap the bolts right off the assembly. It gets much more complicated after that so avoid any unnecessary pressure.Exhaust Leak Sound

Before finally installing the new exhaust manifold, make sure to clean the cylinder head exits with a degreaser sprayer. This helps remove all the carbon buildup in the cylinder heads. Next, bolt the new exhaust manifold to the cylinder heads. Also, don’t forget to spray the bolts and apply the exhaust leak sealant afterward as well. From here onwards, the steps are exactly the reverse of the above-described procedure.

Exhaust Gasket Replacement Cost

An exhaust gasket acts as an airtight seal connecting the cylinder heads to the exhaust manifold. These rings are sandwiched between the manifold and cylinder heads to prevent the extreme temperature (and carbon gases) from escaping.

It is very rare that an exhaust gasket needs to be replaced and can last over 100,000 miles. However, factors such as oil leaking onto the manifold seal can be the subject to a bad exhaust gasket. That said, to fix these gaskets, you should be expecting a cost of around $400 – $500 including labor costs.

But then again, the exhaust gasket replacement cost may differ depending on your car’s model or engine. For instance, exhaust gaskets are measured in diameter sizes like 50, 63, and 76 millimeters. Similarly, the exhaust gasket in your car may require a different diameter size hence the varying replacement costs.

In addition, not all mechanics quote the same exhaust gasket replacement cost. Some may charge an hourly rate of $90 while some can charge $150. So, make sure to visit different mechanics to get the best price.

Exhaust Leak Sound – Frequently Asked Questions (FAQs)

What Does An Exhaust Leak Sound Like

A working exhaust system or manifold considers various aspects such as backpressure and scavenging effect. All of this is done for the smooth outflow of gases from the engine so that the intake is ready for the next cycle. A small leak (or puncture) in your exhaust system can disrupt the smooth outflow of gas. As a result, the exhaust leak produces hissing and deep, gurgling noises from underneath your car. Even though the deep rumble of an exhaust leak may make your vehicle sound like a racecar, it can be very detrimental to your engine’s health.

How To Fix Exhaust Leak

Fixing an exhaust leak depends on several factors. Before fixing an exhaust leak, the source of the leak must be identified. Not all cars have the exact same spot of an exhaust leak. Some exhaust leaks require greater attention whilst some leaks require lesser attention and can be fixed with just a bit of solvent. For instance, fixing (or replacing) an exhaust manifold is quite a lengthy process. it involves removing the exhaust gasket, cleaning the carbon from cylinder heads, and reinstalling the manifold back in its place. Likewise, fixing an exhaust leak on an exhaust flex pipe is a much simpler task. It just involves welding the defective flex pipe and installing the new one and you’re good to go. In the same way, there are other different types of leaks that require much different attention such as catalytic converters, mufflers, and resonators.

Are Exhaust Leaks Bad

Yes, an exhaust leak, particularly, an exhaust manifold leak, can be bad for your (and your engine’s) health. Let’s see how. The O2 sensor, which is located right after an exhaust manifold ends, determines the amount of unburnt oxygen currently residing in the exhaust system. The sensor then sends the data to the ECU which has to monitor how rich or lean the engine is running. However, because of the leak present in the manifold itself, the sensor gives off inaccurate readings. This ECU thinking that the engine is always on high load, injects unnecessary fuel into the injectors. As a result, fuel consumption increases which is how your fuel average drops. Similarly, an exhaust leak before the placement of the catalytic converter can cause all the toxic gas to enter your cabin. This is the reason why you constantly smell car exhaust fumes in your cabin

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