While some oil in the inlet manifold is expected, it can also mean there’s a serious problem with your vehicle. Unfortunately, there are several possible reasons behind the oil in your car’s inlet manifold, so you’ll have to be extra thorough when diagnosing the issue.
Here are the possible reasons why there’s oil in your vehicle’s intake manifold:
The positive crankcase ventilation (PCV) valve redirects blowby gases from the crankcase to the engine. By doing so, it allows the engine to consume any unburnt fuel, preventing the buildup of sludge.
When the PCV valve gets clogged, these oily gases can build up, resulting in oil in the air intake manifold.
Also known as oil galleries, oil passages deliver oil to critical engine components, such as the camshafts, pistons, and crankshaft bearings. When they get clogged due to poor maintenance, these passages can cause oil to leak in the intake manifold.
With proper maintenance, some piston rings can last as long as the engine. On average, however, most piston rings are built to last between 100,000 and 150,000 miles.
When they start to wear, oily blowby gases can enter the combustion chamber. All that oil will eventually combine with existing fumes and find its way into the intake manifold.
Most manufacturers recommend cleaning the air filter every year or every 12,000 to 15,000 miles. After every wash, you typically have to apply an oil lubricant to the filter before reinstalling it. Applying too much of this lube can cause the excess oil to flow to the intake hoses and manifold.
Valve seals control the amount of oil that lubricates the valve stem. When these seals wear or crack, the oil can leak into the valves and enter the combustion chamber. In slanted or V-shaped engines, the oil can sometimes enter the air intake manifold.
A faulty fuel injector can indirectly cause excess oil to enter the PCV system and the intake manifold. When a fuel injector malfunctions, fuel can enter the crankcase and mix with engine oil. This can cause oil dilution and overfilling, with the excess oil eventually finding its way into the intake manifold.
Some oil in the intake manifold is fine. If your engine air filter needs a coat of lube, then you can expect to see a small amount of oil in the intake manifold. You can also expect some oil to enter the intake manifold due to blowby gases, especially if your engine is old.
However, too much oil in the inlet manifold can be bad for your engine. It can clog the spark plugs, causing your engine to misfire. In some cases, oil in the intake manifold can also cause your engine to idle roughly, stall, and exhibit other performance issues.
If too much oil leaks into the combustion chamber, it can also lead to a hydrolocked engine, which can seize up at any minute.
The exact price can vary depending on several factors, such as the faulty part causing the inlet manifold leak. If the culprit behind the leak is a damaged PCV valve, then you can expect to spend anywhere from $10 to $560 on parts alone. If your vehicle needs a replacement piston ring, then it’ll cost you around $10 to $530.
Keep in mind that labor costs and other factors, such as your vehicle’s year, make, and model, can affect the total cost.
Repairing an oil leak in the intake manifold can be pricey, especially if it’s done serious damage to your engine. To prevent this from happening again, here are helpful prevention tips to consider:
Dirty engine oil can clog your vehicle’s oil galleries, so be sure to change your oil regularly. Depending on your vehicle’s year, make, and model, you typically have to get an oil change every 5,000 to 7,000 miles.
When cleaning your air filter, be careful not to add too much oil. Most air filter kits will specify how much oil you need to apply, so be sure to follow instructions.
Some drivers also recommend switching to paper air filters to eliminate the risk of excess oil entering the intake manifold and potentially damaging the mass air flow (MAF) sensor.
Some vehicles aren’t great at getting rid of oily gases, and if this is the case for your car, then installing a new PCV valve probably won’t be enough. To prevent oil from building up inside the intake manifold, consider investing in a catch can.
An oil catch can is a metal container that traps oil fumes before they can enter the air intake system. You’ll have to regularly empty the can when it gets full, but it’s better than letting oil build up in the inlet manifold.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.