Oil in Intake Manifold: The Reasons and Consequences

All cars, except for the electric vehicles, have an internal combustion engine. It means that the car moves forward due to a series of small explosions inside the combustion chambers. For the explosions to take place, a proper amount of fuel and air mixture has to be in those cylinders. Here comes the intake or inlet manifold. It is a series of tubes that evenly distribute the air into the cylinders. It is bad news when there is oil in intake manifold. Why does this happen and what problem it can lead to?

The Reasons for Oil in Intake Manifold

The inlet manifold passes the air to the cylinders through some valves. These valves open at the beginning of a cycle, then close down when the air is through, and then open again at the beginning of the next cycle. When you find oil in intake manifold, you should check:

oil in air intake
A light oil coating is nothing dangerous. (Photo Source: volvo4life)

The Positive Crankcase Ventilation (PCV) Valve

It is the first component to look into when the problem occurs although you should not be worried if there is a small amount of oil in air intake.

It is not rare to have blocked PCV valves on cars with less than 100,000 mileage. You have to examine the entire PCV system. A faulty one will cause an imbalance of air flow and send some oil in air intake. It will also cause the check engine light to come on. Cleaning or replacing is the option if one or multiple valves are completely blocked or semi-functional.

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Clogged Oil Passage

If you never change the oil in your car, it will collect sludge and deposits and leave them in the oil passage. When oil cannot pass freely through the passage, it gathers inside the top of the cylinder head.

When the passage is totally blocked, the oil will go through the PCV valve and enter the air intake manifold. What you have to do to get rid of this problem is to pour an engine flush formula into the oil and run the engine for a few times. When the buildup is cleared, change the engine oil and don’t forget to replace the air filter. If it does not solve the issue, take the help of a professional mechanic.

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Oil in Intake Manifold: How Serious Is the Problem?

There is nothing to be worried about if it is just a light coating of oil. But, a puddle in the inlet manifold takes the issue to another level. In most cases, it indicates to a worn out engine that cannot function at the full force.

The problem does not warrant any immediate action because it will not lead to anything fatal very soon. But, it does mean that your engine is getting old and you probably have to change several components. It will be better to have it diagnosed in an auto servicing shop. They can suggest better which parts need changing or fixing.