6 Symptoms of a Bad Intake Manifold (& Replacement Cost)

The intake distributes air and the fuel mixture between the cylinders. Here's how to tell if your intake manifold is bad or cracked

Air Intake Manifold Car

The intake manifold is responsible for the precise distribution of air into the engine cylinders for perfect combustion.

Therefore, the intake manifold plays an important part in the performance of your car engine.

Unfortunately, the intake manifold fails sometimes – but what happens if it does, and how much will it cost to get it fixed?

In this article, we will discuss the most common symptoms of a bad intake manifold and how much it costs to replace or fix it. Let’s go take a look at the signs first!

The most common symptom of a bad or cracked intake manifold is rough idle together with a check engine light on your dashboard. You may also notice a loss in engine performance together with misfires. In rare cases, it may cause an external coolant leak.

Here is a more detailed list of the most common symptoms of a bad or cracked intake manifold:

Bad or Cracked Intake Manifold Symptoms

1. Check Engine Light

Check Engine Light Reset Itself

The engine control unit is constantly monitoring your car’s sensors while you are driving it, and if any of them is sending wrong values compared to the pre-set values – the check engine light will appear on your dashboard.

If you have a bad intake manifold, the air-fuel mixture will get different than what it is supposed to be, and therefore the check engine light will show up on your dashboard.

When the check engine light shows up – there is also a trouble code stored in the engine control unit that you need to read to continue the troubleshooting.

2. Misfires


When there is a crack or a coolant leak of the intake manifold, it will result in an extra amount of air compared to fuel entering the combustion chamber. This will result in misfires – which happens when the combustion process got disturbed and not completed.

This can also happen due to coolant water in the cylinder coming from an internal crack in the intake manifold or around the intake manifold gasket. If you have misfires, you will also often find a related trouble code in the engine control module.

Learn more: 5 Symptoms of a Bad Intake Manifold Gasket

3. Rough Idle

Car Engine Rough Idle

As you may know by now, a bad or cracked intake manifold will cause the air-fuel mixture to go bad. A bad air-fuel mixture can also cause your idle to become rough.

The engine is susceptible to problems at idle because it needs to run perfectly to hold a steady RPM. This is why you will most likely first notice an intake manifold problem at idle.

4. Loss in Engine Performance

Slow Car

When the intake manifold fails, the fuel and air ratio is affected. We all know how important the air-fuel mixture is for efficient combustion, so any effect on this mixture can affect your car’s fuel consumption.

You will find that it will burn more fuel, and you will have to refill the fuel tank more often. Not only that, but you will also feel that your car is not accelerating properly and that the engine may have hiccups.

Whenever this happens, you need to check the intake manifold for any signs of leaks.

5. External coolant leaks

Coolant Leak

If the intake manifold suffers from an internal crack or a problem near the intake manifold gasket, the coolant can start to leak out in the engine bay.

If you have a pool of coolant under your car after a night in the garage, it is definitely time to check for any signs of leaks around the intake manifold.

Often the leak comes from under the intake manifold, which can be really difficult to spot.

6. Engine Overheating

Engine Overheating

If the intake manifold has a crack and causes the coolant to pour out in the engine bay or into the combustion chamber, the engine’s first effect starts to overheat due to the loss of coolant.

You will see this while driving when the temperature gauge rises on your dashboard, and it is advisable to see the mechanic as soon as this happens, as an overheated engine can seize up and stop working completely.

The best way to detect this is to check the coolant level in the engine bay regularly, and if you notice that it has slowly started to decrease – it is time to check for coolant leaks.

Learn more about overheating here: Overheating car engine.

The Function of the intake manifold

Intake Manifold Function

The purpose of the intake manifold is to deliver an even amount of air into the car engine’s cylinders.

In older cars, the carburetor injected fuel before the intake manifold, and for these engines, the intake manifold needed to spread this fuel evenly.

Newer cars inject fuel at the end of the intake manifold with fuel injectors, and the even spread is not as important anymore as before.

Newer cars do even have swirl flaps inside them, creating a nicer air-swirl when entering the combustion chamber, which creates a more efficient engine.

Intake Manifold Location

Intake Manifold Location

The intake manifold is located on the cylinder head on one side of the engine. In V-engines, the intake manifold is located in the middle between the cylinder heads.

The intake manifold is very easy to spot in most car engines because it is often installed high up in the engine bay.

In some cars, you need to remove some plastic covers to see it first, though. They are often made of plastic or metal so look out for some part, looking like the picture above, to spot it.

If you know how many cylinders your car has – look for a part with the same amount of pipes as your car’s cylinders.

Intake Manifold Replacement Cost

The average intake manifold replacement cost is between $300 and $1100, depending on the car model and labor costs. An intake manifold costs $200 to $600 and the labor costs $100 to $500.

This cost differs a lot depending on the car engine and car model you have. It also depends if you are looking for OEM or aftermarket parts.

The cost of the intake manifold is often the pricey one, so if you want it a little bit cheaper, you can often look for used intake manifolds. The intake manifold is most often a piece of iron, and not many things can fail on these.

However, some intake manifolds, especially on newer cars, have intake flaps inside of them, and in this case, you have to replace the whole intake manifold.

The time of replacing the intake manifold often takes around 1-2 hours if you have some basic knowledge and want to do it yourself. Some intake manifolds have flaps that need to be programmed after an intake manifold replacement – especially European cars.

Still have questions?

Ask any car question in our new community!

Written by:

Magnus is the owner and main author of MechanicBase. He has been working as a mechanic for over 10 years, and the majority of them specialized in advanced diagnostics and troubleshooting. Certified Automotive Diagnostic Technician.