Oil in Intake Manifold, Causes and Fixes

Every car has its exhaust and intake manifold. The latter is the one that has been taking a good volume of air in burning the fuel. The exhaust manifold, on the other hand, passes the burned gas over a catalytic converter going to your car’s exhaust tube. In every scenario, it’s the intake manifold that requires frequent cleaning and inspection.

A lot of car owners within my neighborhood have been asking me for help because their engine oils reduced, and they have to add more. It’s too expensive and heavy for their pockets. They don’t know where the problem is or what causes the issue.

As an auto mechanic, what I do is checking the air cleaner sift and spark plug. Then, I will check whether there’s a leak or not. For the final resort, I will run a compression & an emission test to confirm my suspicion.

In this post, I would like to say something about oil in the intake manifold and how to get rid of it.

Why Is There Oil in Intake Manifold?

How does oil get into the intake manifold? You might be asking. Well, this problem takes place due to the following:

1. Blocked Air Cleaner Filter

Clean air is very important, even for your car. As an auto mechanic, I’ve been advising my clients to keep clean air available for their cars to ensure great engine performance. Yes, it’s for the engine’s sake. With my years of experience in this industry, I’ve learned that various or almost all engine makers like Toyota, Honda, and BMW specialize and give more attention to the significance of car air cleaner.

Those companies I mentioned are using Turbocharger for their engines to guarantee the best when it comes to performance with minimal fuel cost. Of course, they know we want to save money on fuel while we enjoy a smooth and fast ride whenever we go to work or somewhere else. We should do our part, and that is to check and pay attention to turbochargers.

Your car has it. This thing is run by the power of the motor exhaust gas. Therefore, it’s the exhaust system that needs more focus to make sure it stays in good condition. If not, your car’s turbo will fail to do its job well.

With some hints and tricks, you will be sure that your turbocharger’s life will extend. The same for the engine’s life. Both things will get better, saving you from costly and preventable repairs.

Your car’s air cleaner might be clogged or jammed if you feel the engine is not taking enough air. If that is the case, the gas will continuously penetrate your combustion chamber. That is why your engine sometimes emits black smoke. It can even be smelly.

Exhaust gas emitted by your vehicle can also make the bearing of your turboshaft bush weaker day after day. Eventually, the problem will turn into oil in intake manifold over the turbo. Thus, I string recommend cleaning the air cleaner or changing it when necessary. At a cheap cost, it will save you from major repairs. Likewise, it will extend the life of your engine and turbo.

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2. Malfunctioned PCV Valve

Another possible reason behind the idea “oil in my air filter” could be the faulty PCV valve. Check it as soon as possible once you suspect oil is in your intake manifold. A congested PCV valve in your car isn’t a seldom case anymore.

I advise you to check the PCV system in general. Do it properly and carefully to see where the problem is. If it’s the PCV valve causing the problem, then you should change it as soon as possible because a malfunctioning one can trigger imbalanced airflow. The issue can cause some soil to penetrate your air intake. Aside from that, if the PCV valve has any other issue, it will trigger your check engine lighting to appear.

The best solution I can recommend is only cleaning. For minimal clogging, cleaning will suffice. However, if the clog is way impossible to correct with cleaning, then you should take your car to a good mechanic. 

3. Congested Oil Passage

Rusty oil and sludge will accumulate in your oil passage once you fail to change the engine oil. If the oil cannot easily pass over the passage or the passage has been extremely blocked, then the oil will go over your PCV valve. Eventually, the oil will go to the air intake manifold.

The topic you are interested: How to change the intake manifold gasket

4. Damaged Piston Rings

One more possible cause of motor oil entering the intake manifold is the worn or damaged piston rings. You can see the piston rings on the external edge of your pistons in the car’s combustion chamber. These rings are designed to form the combustion ratio. Also, they allow small amounts of the motor oil to lubricate the interior combustion chamber with every piston stroke.

With their daily operation, these rings will inevitably wear out. They’ll loosen and trigger oil blow-by.  The blue smoke emitted through the tailpipe of your vehicle while you drive indicates that your piston rings are already worn out.

At first, damaged piston rings cause too much oil blow-by to lead to excess pressure that will form within the crankcase. When that happens, more engine oil will go over your PCV valve. Finally, the leaking oil will go and enter the air intake, causing further issues in your car.

How to Prevent and Stop Oil in Intake Manifold?

Like I said before, I suggest frequent cleaning of the intake manifold and air cleaner of your car. Simple things can help prevent the engine oil from leaking to somewhere in your car, especially to the intake manifold.

If you notice any of the possible causes I mentioned above or you suspect one or two of them happening to your vehicle right now, don’t waste your time. Don’t try to fix the problems with your bare hands if you have no automotive skills.

Feel free to ask help from an experienced automotive mechanic in your area. That’s the best action to take in this scenario. This way, you can get extra tips that will help prevent the same issues from happening again.

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1 thought on “Oil in Intake Manifold, Causes and Fixes”

  1. Great post, James!

    Very concise and helpful when you attached short solutions for each cause.

    But from what I know, there are other causes for this problem as leaky valve seals, worn out camshafts, and malfunctioning fuel injectors. What do u think?


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