Finding oil in your spark plug wells is alarming, but try not to stress too much (but do take it seriously). Oil leaks happen, and the oil is not always going to makes its way down to your driveway or garage floor.
In this article, we’ll look at the most common reasons you’re seeing oil accumulating inside your spark plug wells and how you can correctly determine the root cause. The fix may not be as bad (or expensive) as you may think.
Top 5 Reasons Oil Leaks Into a Spark Plug Hole
Later, we’ll touch a bit on the symptoms you may experience to lead you to the conclusion that there’s oil in the spark plug chamber, but first, let’s look at the most common causes of engine oil getting into a spark plug hole.
1) Worn Valve Cover Gasket
The engine has a metal part on top of it called a valve cover. A valve cover gasket sits between this cover and the top of the engine cylinder head. This keeps the engine sealed so that oil does not leak from it.
However, all the heat from the engine will wear down the valve cover gasket as time goes on. It will eventually start to crack and become hard or brittle, which then allows oil to leak through the gasket.
You can simply replace the leaking valve cover gasket if you catch the problem fast enough. Otherwise, your engine may suffer permanent damage due to insufficient oil.
2) Old Valve Guide Seals
Vehicles depend on valve guides to assist in managing the intake of air into the engine. Basically, the valve guides secure the valves during the operation of the engine. The only problem is that valve guide seals eventually start to wear out as you continue using your vehicle.
At some point, you will likely need to replace them because bad valve guide seals will not be able to prevent oil from leaking into the spark plugs. Once that happens, you could have a lot of problems with your engine that will cost thousands of dollars to repair.
3) Bad O-Rings
Under the spark plug tubes, there are O-ring seals. Once an O-ring becomes worn out or damaged, oil will leak through and make its way to the spark plug tube. You’ll need to fix this problem quickly before the engine is affected too much.
And since the oil saturates the spark plugs, you’ll need to replace the spark plugs as well.
4) Bad Piston
A piston can crack if it gets exposed to too much heat. Then it will start to make knocking sounds and rattle quite a bit. More important, a bad piston will let oil leak into the spark plugs and that will create all kinds of problems.
Your engine will misfire frequently, and you’ll experience a weaker engine performance. These are all things that will ruin your engine if the piston is not replaced promptly.
5) Bad Piston Rings
Piston rings exist on the top and bottom of the pistons of an internal combustion engine. The purpose of the compression rings is to stop oil from entering the combustion chamber and to remove extra oil that gets onto the cylinder walls.
However, if you have worn out piston rings, then they won’t be able to stop oil from flowing toward the spark plugs. You’ll also see blue exhaust and there may be a smell of engine oil that consumes the cabin.
Signs That Oil Leaking Into Spark Plug Wells
When oil leaks into your spark plug wells, you’ll likely notice several symptoms that indicate an issue. Keep an eye out for the following signs, which could be caused by oil finding its way into your spark plug wells:
Misfires and Engine Problems
Misfires are a common symptom of all sorts of engine issues and oil in your spark plug wells is one of them. This oil can interfere with the spark plug’s ability to ignite the air-fuel mixture, leading to incomplete combustion and engine misfires.
Notice blue smoke coming from your exhaust? This happens because the excess oil is being burned off along with the fuel. When you see this smoke, it’s time to investigate further and fix the issue.
Increased Fuel Consumption
When oil affects your spark plugs, it can throw off the air-fuel mixture in your engine. This can lead to your vehicle burning more fuel than it should, resulting in reduced fuel economy and potentially harming your gas mileage.
Oil in the spark plug holes can also cause your engine to backfire. When this happens, you might notice a loud popping noise and a jolt when you’re accelerating or decelerating. This can be quite alarming (and annoying), but fixing the oil leak should help alleviate this problem.
If you notice a strong gas smell coming from your engine or exhaust, this can be a sign that oil is leaking into your spark plug chambers. The improper air-fuel mixture can lead to excess gasoline being present in the exhaust, giving off a noticeable odor.
Identifying the Leak Source
If you discover engine oil in your spark plug wells, pinpointing the origin of the leak is the most important thing to address the problem.
Start by inspecting the valve cover gasket – cracked or brittle gaskets are a common culprit as heat and age degrade the seal. Valve guide seals are another likely source, especially if they haven’t been replaced in some time. As seals wear out, oil can slip past into the cylinders.
Also examine the piston rings – worn rings fail to contain oil, allowing it to drip into the combustion chamber. Cracked or damaged pistons themselves may also leak if exposed to excessive heat.
Finally, look for compromised o-rings under the spark plug tubes that could permit oil to seep through.
Thoroughly checking these common problem areas and components can help accurately identify the root cause of an oil leak into spark plug wells. Focusing repair efforts on the specific point of leakage, rather than symptom management, provides a lasting solution.