Exhaust manifold leak simply means toxic gases going back inside your vehicle instead of exiting it.
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In the vehicle’s combustion system, fuel has to be burnt to generate the necessary power for the car to move. When the fuel burns, toxic gases come out as a byproduct. These poisonous gases have to leave the car after going through some cooling and processing.
The exhaust system is responsible for cooling down and cleaning the toxic gases coming out of the combustion system. After that, the exhaust system pushes the processed gases outside of the car.
Any leak in the exhaust system can result in gases going back to the car instead of leaving it. The reverse flow of the toxic gases could cause significant damages if you did not take care of it promptly.
In this article, we will walk you through how the exhaust system works, what might cause a leak in the exhaust system, how to fix the exhaust manifold leak and the associated repair costs.
How does the exhaust system work?
The exhaust system is responsible for moving the gases coming out of the combustion system away from the car. Moreover, it muffles the noises associated with high speeds and explosions in the combustion system. Finally, it cools down the toxic gases and converts it into less harmful gases before exiting the car.
With all this onerous responsibility, the exhaust system consists of specific parts to help it do the job correctly. These parts include manifolds, heat shields, joints, pipes, mufflers, and flexible unions.
The exhaust system experiences the roughest conditions as compared to the other parts of the vehicle.
It must cool temperature from as high as 1,200 degrees to the ambient temperature.
During cold weather, water might come as a byproduct of the combustions system. This water can cause the exhaust system to rust over time.
Moreover, the exhaust system is located towards the bottom of the vehicle, which forces it to face all the different road conditions (e.g., snow, ice, dirt, salt, etc.)
That been said, it is not surprising that you might need to do regular repairs and maintenance to the exhaust system more often than other parts of the vehicle.
Exhaust manifold leak symptoms
Knowing that you have an exhaust manifold leak is easy to catch; however, it is more challenging to determine where the leak is coming from exactly.
There are general symptoms that can tell you there is a leak in your exhaust system, including:
- Strange noises in your engine
- Poor fuel economy
- Engine bay smells like burn
- A reduction in the acceleration power
If you experienced any of the previous symptoms, you might need to confirm the leaks using visual inspection.
Before doing any visual inspection, you need to keep in mind that the exhaust system can be boiling, especially if the car was running. Therefore, before doing any investigation, you need to make sure that the vehicle has cooled down for at least a couple of hours. It is a good idea to wear safety gloves when doing the inspection.
Once your vehicle cooled down, open the hood and find the manifold. It might be a little tricky to find the exhaust manifold as it could be hidden under heat shields. The manifold is usually close to the exhaust pipe (one of the multiple rusty pipes).
Follow the exhaust pipes and check for leaks or cracks, as you follow. Make sure to check all the exhaust system components (e.g., catalytic converters, muffles, resonator, etc.) check for leaks from the bottom of the top using a mechanic mirror.
What does the exhaust manifold leak sound like?
It is a good idea to check for a manifold leak by listening to strange specific sounds.
The exhaust manifold leak sounds like tricking or puffing, and the sound gets louder when you get closer to the catalytic converter or the engine.
Start the engine and have a friend rev in the motor and see if the sound gets louder of changes. Monitor the noises in the exhaust pipes.
Remember, the exhaust system can be boiling, therefore, never touch the pipes with your hands. Make sure to wear safety gloves.
Consequences of exhaust manifold leaks
As we mentioned before, if there is a leak in the exhaust manifold, the toxic gases will go back inside the car instead of leaving it.
Depending on the location and severity of the leak, the reversed behavior of the gases flow can cause many issues, including:
- Disturbing the function of the oxygen sensor
- Affecting the fuel trim
- Causing improper functioning of the EGR valve
- Might result in catalytic converter failure
- Damaging the exhaust valves
What causes exhaust manifold leaks?
There are three leading causes for a manifold leak:
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A leak in the manifold gasket
As we mentioned before, the gas flowing in the exhaust system can be extremely high. Then when the car cools down, the exhaust system’s temperature drops dramatically.
This cycle of heating and cooling can cause all parts of the exhaust system to expand and shrink in a sequence.
The expansion and contractions can cause cracks and breaks in the gasket.
The manifold gasket is responsible for sealing the entire exhaust system. If the gasket got damaged or cracked, the gases are going to leak back to the car, which affects the car’s overall performance and causes strange noises in the engine.
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A crack in the manifold itself
Like what might happen to the manifold gasket, the manifold itself might crack due to the heating and cooling cycles of the exhaust system.
A small crack in the manifold might not be noticeable. It can cause strange sounds right when you start the engine. These sounds are reduced by the time you drive as the metal parts expand with heat and close the cracks.
However, if the cracks get bigger and bigger, the metal expansion can not close the cracks and significant engine failures are likely.
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Broken or loose manifold bolts
The manifold is connected to the exhaust system by two large bolts. These bolts might get loose or break due to the continuous heating and cooling or due to the wear and tear over time.
Loose or broken manifold bolts can cause holes and therefore leaks in the manifold, causing the toxic gases to reverse its flow direction.
How to fix the exhaust manifold leak?
Leaking into the exhaust manifold will not stop you from driving your vehicle. However, the leak can cause significant engine troubles in the short run.
If you have some mechanical experience, you can fix the exhaust manifold leak on your own and save the labor cost. However, if you do not have any mechanical knowledge, it is always recommended that you take your vehicle to an experienced mechanic to avoid causing more trouble.
Once you decided to fix the exhaust manifold leak on your own, there is some specific equipment you need to prepare, there is a sure way you need to make your vehicle with, and then you can do the actual fix.
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Tools and equipment
- A brand-new exhaust manifold or manifold gasket (depending on where the leak is coming from)
- Wrenches, socket set, and ratchet
- Jack stand and jack
- A torque wrenches
- Penetrating manifold oil and degreaser
- Gloves and towels
- Your vehicle’s owner’s manual
- A repair manual
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Prepare your vehicle
Fixing any part in the exhaust system requires specific preparation before you start the fixing process.
Since the exhaust system is usually scorching, the first step for you is to make sure that the car has completely cooled down. Then, you need to remove the negative cable of the battery.
After that, you need to make sure that the car is on a flat surface (your garage is the best location for this type of repair).
Then, you will need to raise your car using a jack and let it rest on the jack stand.
With that, you are ready to repair the exhaust manifold leak!
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Find the leak(s) location
As you saw earlier, fixing any issue with the exhaust system requires a little preparation. Therefore, you want to make sure that you set all the leaks at once to avoid lifting the car again and fixing another leak.
That been said, the first step in fixing the exhaust manifold leak is to find the locations of all the leaks.
As a reminder, the exhaust pipes can be extremely hot; therefore, remember to wear safety gloves to avoid injuries.
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Remove the bolts
The manifold is connected to the exhaust system by two large bolts. You might need to dig a little to find these bolts as the system might be covered with heat shields.
The two bolts are usually tightened very well, which means you might need to use a wrench to unbolt them. In some cases, you might need to put some penetrating oil and leave it for about 15 minutes to help easily unbolt the two bolts.
Make sure to carefully unbolt the two bolts as you do not want to damage them or break the heads of the bolts and cause more damages to the manifold.
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Replace the gasket or the manifold
Once you removed the two large bolts, you can now find the manifold inside the engine.
If you want to replace the gasket only, do not fully take the manifold out of the engine. You can simply half-pull the manifold out of the engine, and then pull the faulty gasket out of the cylinder. After that, simply push the new gasket into its slot in the bottle.
On the other hand, if you want to change the entire manifold, you must obliterate it from the engine and insert the new one back inside. It is essential to keep track of how you unassembled the manifold to be able to reassemble it.
How much does it cost to fix the exhaust manifold leak?
In the automobile field, and maintenance cost is divided into parts costs and labor costs, which is measured by the number of hours needed. The labor cost differs significantly by the location of the repair (e.g., dealership versus repair shop).
In general, fixing the exhaust manifold leak requires two to three hours of repair. The average labor cost per hour ranges from $80 to $90, which means that fixing the manifold leak will cost from $160 to $270 on labor only. However, this number can go up to $330 if you want to repair your manifold leak in a dealership where the labor cost per hour is about $110.
On the other hand, you can eliminate the entire labor cost if you fix your manifold leak on your own.
The parts cost depends on the vehicle’s make, model, year, and the number of cylinders in the motor (e.g., four or six or eight). For example, the gasket cost for a Chevrolet Impala ranges from $18 to $28 if you buy it from a local auto repair shop. However, the gasket for the same Chevrolet Impala can cost $50 if you buy it from a dealership.
The bottom line, the cost of fixing your exhaust manifold leak could range from $18 if you set it on your own to $400 if you fixed it at a dealership.
Conclusion
The exhaust system is responsible for cooling, cleaning, and moving the toxic gases out of the vehicle.
If there is a leak in the exhaust system, the toxic gases will reverse its flow and go back inside the car instead of leaving it.
A leak in the exhaust can mainly come from the manifold, which could be due to a leak in the gasket, in the bolts, or in the manifold itself.
You can detect a leak in your exhaust manifold by noticing any burning smell, strange noise, or visible leaks in the exhaust system.
Fixing the exhaust manifold leak on your own can save you lots of labor money and can drop the repair price from as high as $400 to as low as $18. However, if you do not have the necessary mechanic experience, you might cause significant damages that can cost you much more money than the actual repair.