Bad intake manifold gasket vs. blown head gasket

Michael Griskauskas

A blown head gasket will cost more to repair than a bad intake manifold gasket. However, both issues are dangerous and can lead to more car issues like poor fuel economy.

These two components are critical since they are responsible for several functions, such as sealing various engine parts. If the intake manifold or the head gasket gets damaged, then other engine parts will follow suit. This is because they are dependent on the two components’ seal function.

We are going to take a look at:

  1. The intake manifold gasket and head gasket functions.
  2. The two components’ malfunctioning symptoms.
  3. The causes.
  4. The replacement costs.
  5. How to test the two components properly for any faults.

Read more: OBD2 Codes: Free Download, Lookup, Meaning, Fixes, Full List


Intake manifold gasket

The intake manifold gasket is placed between the intake pipe and the cylinder heads in the engine. Its primary function is to seal the intake manifold and the cylinder heads to reduce air leaks.

Air is injected along with fuel into the cylinder chamber to combust. The air entering the cylinder chamber will first hit the shut end of the intake valve, which will cause the air to rush back at high pressure into the manifold runners. The intake manifold gasket is there to prevent the air from escaping by withstanding the high pressures and temperatures in the engine bay.

Head gasket

The head gasket acts as a connector that is located between the cylinder heads and the engine block. The head gasket has machined cylindrical bored holes that accommodate the engine pistons. The primary function of the head gasket is to provide a seal between the block and cylinder heads. It does this by preventing the pressures from the moving cylinder heads from passing through to the block.

The engine block and cylinder heads are often made of two different materials, which means they respond to heat differently. The gasket acts as a bridge between the two to compensate for any uneven expansions and contractions that would have otherwise caused blocks or leaks. It also seals the pathways of coolant and oil within the engine.

Bad intake manifold gasket vs. blown head gasket: Symptoms

blown intake manifold gasket symptoms
The two types of gaskets mostly have the same symptoms, except a bad intake manifold gasket has one more, which is poor fuel economy

An illuminated check engine light (CEL) will normally be present in both scenarios. This will often be the first sign of an issue with your head gasket or intake manifold gasket.

Bad intake manifold gasket

Coolant leaks

The intake manifold gaskets also seal engine coolants. The intake manifold gasket acts as a seal for the air and also a coolant that cools the intake charge. If the gasket gets damaged or wears out due to its age, then the seal will be broken, and the coolant will leak.

Excessive white smoke

The coolant can leak into the combustion chamber, merge with oil, or leak out of the exterior of the intake manifold. When the coolant leaks into the combustion chamber, you will have excessive white smoke because the engine burns the coolant.

If the coolant leaks out of the exterior of the intake manifold, then there will be excess smoke from the top of the engine. That is because the coolant is burning before getting to the engine. You may also see coolant leaks underneath your vehicle.

Milky engine oil

When the coolant merges with oil, you will get coolant deposits in the oil reservoir, reducing your coolant levels and affecting the lubricating functions of the oil. The oil that gets mixed with coolant liquid will often have a milky consistency.

Overheating engine

The engine will start overheating after the coolant leaks have become so severe that there isn’t enough cooling going on in the engine area. You will find yourself adding more coolant at a much more frequent rate than usual. The increased coolant usage will point to a coolant leak and low coolant levels in the reservoir.

There will be an indicator light on the dashboard to show you when the engine is overheating but make sure to look at other causes that may rule out a bad intake manifold gasket.

Engine performance issues

Common symptoms resulting from a leakage in the intake manifold gasket include a stalling engine and a decline in engine performance. When the intake manifold gasket fails, there are two things that can happen:

  • The air leak in, causing a lean condition.
  • The coolant leaks in the combustion chamber, causing the flooded condition.

Once this happens, the engine will begin to function at less optimal levels, which will cause issues like engine stalls and loss of power.

You might experience engine misfires due to poor fuel and air ratios in the combustion chamber. The vacuum leak will also affect your vehicle’s acceleration and lead the engine to stall from time to time.

Read more: P0301 – Cylinder 1 Misfire Detected

Poor fuel economy

If you have a bad intake manifold gasket, more air will leak into the combustion chambers, and there will be a lean condition. The engine will then start to use more gasoline than usual to provide the same power as before. This will cause an increase in the amount of fuel you buy, leading to poor fuel economy per mile.

Blown head gasket symptoms

Coolant leaks

Coolant leaks may signify a blown head gasket but can also be associated with other issues such as a bad intake manifold gasket. Make sure to check the other symptoms. You will notice a pool of coolant liquid on the surface of your parking spot if you have a leaking head gasket.

White exhaust smoke

A blown head gasket can allow coolant to leak into the combustion chamber. It will then get burnt together with the fuel in the chamber to create a thick white smoke that passes through the exhaust.

Milky engine oil

The coolant may sometimes leak into the engine oil if you have a blown head gasket. The coolant liquid will mix with the engine oil and form a milky consistency. This milky engine oil is not favorable for your engine’s operations and should be replaced as soon as possible.

Overheating engine

Overheating in the engine will start once the blown head gasket affects the flow of coolant, allowing it to mix with oil. It can also happen when the coolant leaks outside as less and less of it reach the engine area. The engine will not be cooled efficiently under these conditions and will cause an overheating issue that needs to be fixed immediately.

Engine performance issues

A blown head gasket will lead to high engine temperatures, coolant leaks, and poor air to fuel ratios. This will affect the performance of the engine by creating poor combustion conditions and inconsistent burns. Your car will start experiencing rough idles, engine stalls, and a drop in acceleration.

Bad intake manifold gasket vs. blown head gasket: Causes

bad intake manifold gasket
A blown head gasket has the same symptoms with a bad intake manifold gasket, with one addition of the detonation in the engine

Bad Intake manifold gasket causes

Most intake manifold gaskets are built to last between 60,000 and 80,000 miles, after which they will start to experience some form of failure. Different intake manifold gaskets will take different periods to get worn out. Plastic materials and poor designs are the biggest contributors to how fast the part can age. Your vehicle may have a bad intake manifold gasket if it has been used for more than 80,000 miles.

Heat is the major cause of a faulty intake manifold gasket. Increased heat in the engine bay can lead to the expansion of the cylinder heads. The expanded cylinder heads will bulge into the gasket, thus breaking it.

Blown head gasket causes

The head gasket can get blown in three ways: from old age that causes wear and tear, if there is a detonation, or if the engine temperatures are too high. Extreme heat conditions in the engine bay will cause the engine block and cylinder head to expand beyond their limits. Detonation inside the engine will increase the pressure inside the chamber, which will, in turn, affect the head gasket.

How long can I drive?

Bad Intake manifold gasket

You should not continue driving a vehicle with a bad intake manifold gasket even if the car is still running.

The symptoms of the lousy manifold gasket, such as overheating in the engine, will result in a cracked engine block that is costlier to fix than a malfunctioning intake manifold gasket. However, if you are not yet experiencing coolant leaks and the vehicle is not stalling or running rough, you can drive it for a few months.

Blown head gasket

It is entirely unsafe to drive with a blown head gasket. You should take the vehicle to the mechanic shop to get the problem fixed as soon as possible as the issue can be a fire hazard and lead to expensive car repairs like engine replacements.

A blown head gasket will inevitably damage your engine, and this will happen faster when compared to the effects of a bad intake manifold gasket.

A blown head gasket will affect the engine in a few weeks or even days, depending on the driving conditions and the extent of gasket damage. Regardless of the driving conditions, you should take the vehicle repaired the moment you notice a blown head gasket.

Intake manifold gasket vs. head gasket: Replacement cost

The good news about the intake manifold gasket is that it is inexpensive and will not break your bank to get it replaced. The intake manifold gasket is often made from relatively cheap materials like plastic, rubber, metal, or a mixture of these materials.

For that matter, replacing the intake manifold gasket will set you back an average of $20 to $120, depending on the material, vehicle model, and gasket design. You will also be charged for the labor cost by your local mechanic, which will cost you an average of $170 to $420. The total replacement cost will be between $190 and $540, which is fairly affordable for most car owners.

A blown head gasket is one of the most expensive parts to replace in any vehicle. This is why it is important to fix blown head gasket issues, such as coolant leaks, as they arise.

The replacement costs run into thousands with the average cost ranging from $1000 to $2000. The high cost is because of the labor involved rather than the price of the head gasket. The replacement procedure is time-consuming and labor-intensive since it consists of removing and replacing the engine head.

Bad intake manifold gasket vs. blown head gasket: How to test

Two tests are used to determine the condition of the intake manifold gasket and the head gasket: compression and leak-down test. The compression test shows how much pressure the engine produces, and the leak-down test shows how well the engine holds that pressure.

Compression test

The compression test is an easy test you can do at home using a compression test kit. The kit is used to measure the compression of each cylinder to check for any wear in these components; valves, valve rings, cylinders, and springs. A 15% and above compression variation will point to a blown head gasket, broken valves, cylinders, valve rings, or springs.

Here are the steps you should follow:

  1. Turn up the engine to normal operating temperatures and then proceed to disconnect the sparkplug leads.
  2. Let an assistant help you by pressing on the accelerator pedal in readiness to ignite the starter.
  3. Proceed to disconnect the sparkplug and connect the compression tester to the sparkplug hole.
  4. Tell your assistant to ignite the engine for about six to eight seconds to reach the maximum pressure.
  5. Take a note of the readings on the pressure gauge to ensure they remain within 10% and 20% of the manufacturer’s recommended reading (usually about 100 PSI). Perform the same test for all cylinders to see which one is worn.
Watch this video to see how a compression test is done.

Leak-down test

The leak-down test measures the rate at which compressed air leaks out of a cylinder and can be used to identify a bad intake manifold gasket and a blown head gasket. This test is done by pushing compressed air through the cylinder, measuring the amount of air getting in and out, and calculating the rate at which air leaks using the loss difference. The steps are also straightforward, and you will need a leak-down test gauge kit.


  1. Disconnect the sparkplugs and make sure the cylinder to be tested is at the Top Dead Center (TDC). You will do this for all the cylinders you want to test.
  2. Find a spark plug adapter and connect the gauge kit to the hole.
  3. Proceed to connect compressed air and turn on the regulator to pressurize the cylinder.
  4. Take note of the readings on the gauge and compare them to the manufacturer’s recommended readings for normal operations.
  5. You will also need to pay attention to the flow of the compressed air to see where the air is escaping from; intake valve, exhaust valve, piston rings, head gasket leak, intake manifold gasket, or a cracked cylinder head. This will be noticed by a hissing sound close to that part.

Look at the readings and note the percentage loss in each cylinder. If there is a big difference (normally between 15 and 20 percent) in one cylinder then the issue lies in that cylinder. However, if multiple cylinders show a loss that is more than 20 percent, especially in adjacent cylinder, then the issue may lie in the head gasket or the intake manifold gasket.

Watch this video to see how you can perform a leak-down test.


As you can tell, the best thing to do when faced with a bad intake manifold or a blown head gasket is to fix the issue as soon as it arises. You may be able to drive the vehicle longer with a bad intake manifold gasket, but the fault will eventually lead to more expensive problems.

On the other hand, an ignored blown head gasket will be dangerous and costly, especially if it leads to an entire engine rebuild or a replacement head gasket. The first symptom of a blown head gasket is usually a minor leakage that can be permanently repaired with a sealant. Take advantage of early warning signs to avoid costly repairs for the head gasket and the intake manifold gasket.

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