Intake Gasket – How To Detect These Leaks?

Intake Gasket – How To Detect These Leaks?

Have you started experiencing some weird symptoms in your car like the check engine light, rough idle, hissing noises, and other strange symptoms? Well, maybe it’s your intake gasket and you have a manifold leak. If you suspect that option, then you are at the right place because there will be a lot to cover on this topic.

Having a problem like this can be a real pain to deal with. Namely, because this intake gasket has a significant importance when it comes to the proper work of the engine. If this component is faulty. It could basically ruin the performance of your engine and make your car drive very poorly.

So, in order to learn more about this intake gasket and the manifold leaks, you need to start understanding more about these components and how they look, and what are their goals. Knowing their method of action and where are they located will help you pinpoint problems concerning them. That’s why we are going to help you out.

First, we will learn what is an intake gasket and then we will cover why it is so important. Then we will learn more about the manifold leak and the intake manifold gasket symptoms. Later on, in the article, we are going to cover how you can diagnose and fix the problem. So, if you are interested in learning more about this problem, follow along.

What Is An Intake Gasket?

Now let’s cover some of the basics and that is to learn what is an intake gasket. I bet that there are a ton of people out there who are not into cars and do not know about this component or possibly confuse it with another component that does a similar role. This is why this chapter is dedicated to them and learning more about the intake gasket in general.

So, what is an intake gasket? Well, an intake gasket is a gasket that lies between the intake ports of the cylinder head and the intake manifold.

If you run an inline engine, you probably have one intake gasket that goes along the whole block. But if you have a V-style engine like a V6 or a V8 for example, it means that you have two of these gaskets on your engine because you have two cylinder heads.

Many people confuse this gasket with the head gasket and that is totally wrong. The intake gasket is also known as the manifold gasket is usually a light rubber gasket that is mounted between the intake manifold and the engine head as we mentioned.

While the head gasket is mounted between the engine head and the engine block. This gasket is a different type of beast and it is really heavy duty and designed to withstand the immense heat that is created in the engine block. So, don’t confuse the two.

Another thing to add is that this type of gasket is usually made out of rubber, or paper. They are fairly inexpensive to replace and you can do it in your garage using socket wrenches. Later on, we are going to explain how it is done. Now let’s learn more about the importance of this intake gasket.

Why This Intake Gasket Is So Important?

Now let’s learn more about the intake gasket and its importance. What role does this intake manifold gasket play and why we cannot live without it? Let’s elaborate.

Even though this gasket is simple and cheap, it could create a ton of trouble for you as a car owner. This is the case because this gasket has a role to maintain a proper seal between the intake manifold and the cylinder head.

There just needs to be a proper seal between the two engine components and this gasket’s role is to do that.

This is one of the most crucial roles in our car, to make sure that everything is sealed well and there are no coolant or air leaks.

Intake Gasket

These components often don’t age well. Rubber becomes old and brittle, it will start to allow air or coolant to pass through. Similar to the paper gaskets. Even though the second type is much more effective in preventing leaks because this gasket can stand a lot more beating than the rubber ones.

The type you are running depends much on the engine that you run. Let’s say that you have a Chevy V8. Then you highly likely will be having problems with this gasket because it is all made out of rubber and it will fail after some years of use.

But have you asked yourself what is the main problem with these gaskets? What sort of trouble they could cause you? We are going to cover the main problem in the following chapter before we dive into the symptoms of a bad intake gasket.

Manifold Leak

Now let’s discuss the elephant in the room when it comes to a bad intake gasket and that is the intake manifold leak. What does this mean? Is some fluid leaking from somewhere?

Yes, there are ports on the cylinder head that allows coolant to enter and cool off the intake. But this is not that frequent. Nowadays cars do not run coolant to the intake. But as you probably know, air can leak as well. And in this situation happens precisely that. Unmetered air is entering the engine because of this bad gasket on your vehicle.

But you could also lose air from this place as well. And this is no good because you will face a lot of intake manifold gasket symptoms that will be present when this damage to the gasket happens. More on these symptoms we are going to cover in the following chapters.

What is important here is to learn how to diagnose this issue and sort it accordingly. Without this, you could end up with damage to components such as the spark plugs, O2 sensor, and catalytic converter because it is highly likely that your engine will run lean when this problem happens. Not to forget the other symptoms.

But more on that in-depth, we are going to cover in the following chapters.

Another thing to add is the relatively inexpensiveness of the intake gasket. It will not cost you more than $30 for both sides if you have two of these gaskets.

What is also worth noting is that it is a relatively simple job that requires moderate mechanical knowledge. So, if you are into cars you will tackle it in no time. But more on that later on, now let’s cover the intake manifold gasket symptoms.

Intake Manifold Gasket Symptoms

Now let’s dive into the intake manifold gasket symptoms since that’s why we are here in the first place. Knowing the symptoms will help you determine that you have a problem with the intake gasket on your car or truck.

This will be really helpful because there are a ton of mechanics out there that are not that experienced in finding these vacuum leaks and will misdiagnose stuff with you ending up paying a ton of money to get things sorted out. And frankly, you don’t want to be one of those people. That’s why follow us carefully while we cover the intake manifold gasket symptoms.

1. Check Engine Light

The first in our list of intake manifold gasket symptoms is the check engine light. This will be the most common symptom when you are having a bad intake manifold gasket.

The check engine light will probably greet you soonest when you start experiencing some issues with this gasket. So, why is this the case?

Well, this will be the case because there will be a vacuum leak when this gasket fails. And wherever there is a vacuum leak, there will be some symptoms and the check engine light will be one of them.

Intake Gasket

What you can do in this situation is to diagnose the check engine light with an OBD2 code reader and learn more about these codes. When it comes to this type of problem, you will highly likely be getting a problem with the air mixture. More precisely, there will be a lean situation when there is too much air and too little fuel.

So, the most common codes when it comes to this type of situation are the codes P0171 and P0174 which indicate problems with the mixture. There will be also codes for the MAF sensor in some cases as well when it comes to the intake gasket. So, make good use of that OBD2 code reader.

On the other hand, if you have a coolant leak, you will have a problem with your catalytic converter and the O2 sensor, these components will get damaged and you will get codes concerning the O2 sensor or a code about the catalytic converter such as the P0420 or P0430. Now let’s move to the next probable intake gasket symptom.

2. Lean Air To Fuel Mixture

The second situation when you have an intake gasket leak as we hinted above will be the lean air to fuel mixture.

This lean air to fuel mixture is basically the consequence of the vacuum leaks in your intake manifold.

There is some unmetered air that enters the engine from these intake ports and this will attribute to poor engine work and also issues of the engine keeping afloat and running properly.

When this happens, you will get a check engine light with the codes P0171 or possibly P0174 as we mentioned above. Now let’s continue with the other intake manifold gasket symptoms.

3. Intake Manifold Leak Sound

Now when we cover the intake gasket and the intake manifold gasket symptoms, it is worth mentioning the sound that there will be a frequent occurrence.

This sound is resembling a hissing noise. The moment that you put your foot on the throttle you will hear some hissing coming from the top of the engine. This actually is a great sign for you because you know that you are dealing with an intake gasket leak or some other vacuum hose leak. The only thing left is to find it. But more on that later on.

4. Engine Misfires

Another in our list of intake manifold gasket symptoms is the situation when you have an engine misfire. Engine misfires will be present a lot when you are dealing with a bad intake gasket. So, why is this the case?

If you didn’t know, engine misfires are explosions that occur in the cylinders. But these explosions are either premature or delayed. This means that they are not timed right.

So, when there is bad timing of the explosions caused by a lean situation, you will have trouble with the engine misfires. Beware of these misfires and make sure that your intake gasket performs perfectly.

5. Rough Engine Idle

The rough engine idle is another on our list of bad intake manifold gasket symptoms. This is mainly caused by the same situation with the lean mixture that we described previously.

In these situations, you will notice how the engine will struggle to keep afloat and the RPMs will fluctuate very often.

They will increase and decrease and this is not good. Whenever your car is idling, it should have about 800 RPM. Anything above this can be an indication of a bad idler control valve, a bad throttle body, or a vacuum leak. And in our case, we have a problem with a serious vacuum leak that is caused by a failing intake gasket.

What is worth noting is that you should check all these scenarios and make sure that your car has perfect idle. Now let’s move to the next symptom.

6. Bad Fuel Economy

The next intake manifold gasket symptom that we would like to cover is the poor fuel economy. This poor fuel economy will be attributed also to the lean situation with the air to fuel mixture in your engine.

The MPG rating of your car will drop quite significantly because you are letting too much air get into the intake with this bad intake gasket. The more air enters the intake the more fuel the computer will decide to drop in the cylinder when this happens.

So, don’t be surprised that along with the misfires and the poor engine work to see a huge drop in the MPG of your vehicle. Now that’s all if there is a vacuum leak in your intake manifold. Now let’s cover the symptoms when there are coolant leaks.

7. Coolant Leaks

The coolant leaks are also worth discussing when it comes to the intake gasket. If you didn’t know, there are some engines that allow the coolant to flow into the intake manifold.

This design is mostly present on older Fords or older design engines that implement steel intake manifolds that are extremely heavy and need to cool down.

On modern cars, there is a relatively low chance that you will notice something like this. So, if you are running a plastic intake manifold then there should probably be no coolant leaks. But still, look for your engine code and see what you can find based on the diagrams for that engine.

If you have coolant leaks, you will notice a formation of rust from the front or at the rear of the engine. Depending much on the design.

There will be rust along the oil valley and when you notice something like this, it is important to act quickly because this coolant could end up damaging your engine and dilute your oil.

So, you definitely don’t want a big sludgy mess in your engine. This is why you need to jump in and diagnose this problem with the leaking intake gasket and make sure that you get it fixed. In the next chapter, we are going to cover precisely where we will learn how this is performed in-depth.

How To Diagnose & Fix An Intake Gasket Leak?

Now let’s get to business and start diagnosing the problem with the intake gasket leak. How you can be able to tell if your intake gasket is leaking?

Well, there are two options for you. Depending on if the gasket is leaking air or it is leaking coolant. In most cases, the gasket will leak air when it starts to show symptoms like the check engine light, misfires, rough idle, etc. Also, there are not a ton of engines that run coolant in the manifolds out there. So, we will focus on finding the vacuum leaks.

And for this, you will need a smoke machine. With a smoke machine, you will be able to pinpoint leaks in your intake manifold and other vacuum lines. So, how you can do that?

Well, it is really simple in most cases, you just unplug the PCV breather hose and stuck the smoke machine hose there. Or possibly remove the snorkel of your intake and plug the smoke machine through the flap of the throttle body.

Just find the closest hose that you can get that enters the intake manifold and place this smoke machine into it. Then the sides of the intake manifold will start to smoke and you will find your culprit.

On the other hand, if we are dealing with a coolant leak, things can be tricker. For this, you will need a pressure tester to locate the leak. Also, check the plugs and see if there are rust deposits on one of them.

But what is most common is the rust buildup and visible leaks from the front of the engine when you are dealing with these coolant leaks. And there will be a lot of it.

Replacing Intake Manifold Gasket

The next thing will be to remove the intake manifold once you diagnosed the problem and perform an intake manifold gasket replacement.

Replacing this component is really easy. You just need to have the right socket keys and remove everything in proper order. Once you removed everything. Clean the intake runners and also the manifold. Apply the new intake gasket and tighten everything up to spec. Replacing it instead of using an intake manifold gasket sealer is recommended if you don’t want to face the same issues all over again.

Intake Manifold Gasket Replacement Cost

So, what is the intake manifold gasket replacement? Well, if you do it by yourself, it will be really cheap. Less than $50 on average. But you will need to have the right tooling for removal and a smoke machine for testing.

Intake Gasket

If you do this at a shop, you will highly likely have to pay about $250 to $350 for all this. Which is not cheap but is still an option.

Facts About Intake Manifold Gaskets:

  1. The intake manifold is an essential component of any vehicle with an internal combustion engine, and it plays a key role in the combustion process.
  2. The intake manifold helps to distribute air evenly to all the cylinders and helps cool down the cylinders to prevent the engine from overheating.
  3. The air from the outside travels past the air filter and through an ECM-assisted throttle body that controls airflow speed.
  4. The air then enters the intake manifold plenum, or main body, connected to the throttle body housing, and is drawn into a set of passageways called runners through the vacuum created by the downward stroke of the engine’s pistons.
  5. The intake manifold is bolted flush and firmly to the engine’s cylinder head with the runners located above the intake valve or valves.
  6. The intake manifold gasket seals the intake manifold to the engine and is typically made from aluminized steel coated in a carbon-based rubber compound.
  7. High-quality intake manifold gaskets are constructed as one piece with reinforced edges and linings around each port or runner opening and must be resistant to decay caused by oils and coolants.
  8. The performance of your engine depends upon the quality of the intake manifold gasket.
  9. Symptoms of a bad intake manifold gasket include coolant leaking from the vehicle, engine overheating, green, red, or yellow leaks under the car, the check engine light coming on, and the engine starting to run rough.
  10. If you notice any of these symptoms, you should consult a professional mechanic for a definitive diagnosis and repair.


In this article, we have covered quite a bit when it comes to the intake gasket. We first learned what is this component and why it is so important.

Then we covered the symptoms that you will face whenever this intake manifold gasket fails and these include the check engine light, misfires, vacuum leaks, etc. Then we learned how you can detect vacuum leaks at home with a smoke machine and how you can fix this problem by yourself.


Now let’s answer some frequently asked questions.

What Is The Intake Manifold

The intake manifold is a device that is installed on the top of the engine. This intake manifold has a tube to each of the intake ports of the cylinder and uses these ports to introduce the air and fuel mixture to the cylinder.

What Does An Intake Manifold Do

The intake manifold basically directs the air and fuel mixture into the cylinders. The valve opens and the mixture enters the combustion and the 4-stroke sequence occurs.

What Is An Intake Gasket

An intake gasket is a special gasket that lies between the intake manifold and the cylinder head. This gasket has a special role to keep the proper seal between the two components and not allow any unmetered air to pass through and enter the combustion.

How To Test For Blown Intake Gasket

You can test for a blown gasket by using a smoke machine. You can remove the breather tube for the PCV system and introduce the smoke into the system. If there are leaks the smoke will start to escape. This is the easiest way to test for a blown intake gasket.

How Much To Replace Intake Manifold Gasket

If you do this work at home by yourself, you will highly likely be paying more than $100. But if you do this job at a shop then the cost will probably be between $250 and $350 depending on the work required.

How To Install Intake Manifold Gasket

You can install this gasket pretty easily. You first need to remove the fuel rails and then unbolt the intake manifold. Then you can remove the intake manifold and install the new gasket in place. And repeat the same procedure in reverse order.

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