Some cars have experienced this situation. When replacing the spark plug, after pulling out the ignition coil, you can see a lot of oil on the ignition coil, and there is also a lot of oil in the spark plug installation hole. What's going on? Is the engine burning oil? This is just a minor issue, not caused by engine oil burning, but by oil leakage from the valve cover gasket. The valve cover gasket is located at the top of the engine, and many cars have oil leakage from this gasket.

Due to the large area and complex shape of the valve cover gasket, as shown in the figure below, there is a whole circle of rubber on the outside and a seal around each spark plug. So any place could be a point of oil leakage. If there is an oil leak in the outermost part of the circle, the oil will flow out directly and be visible to the naked eye. There is a lot of oil on the top of the engine, and if it is covered with dust, it will appear very dirty and look very serious. If there is a lot of oil leakage, it will flow down the engine and all the way to the bottom of the engine. So when you see that there is oil leakage at the bottom of the engine, it may not necessarily be from the bottom components, but it may also be from the top flowing down, and you need to carefully check and confirm. Oil leakage from the outer ring of the valve cover gasket is the most common phenomenon.

If the gasket near the spark plug leaks oil, the oil will not flow outside the engine and will directly flow into the spark plug hole. Of course, it will not flow into the cylinder because there is a spark plug blocking it, and it will only accumulate more and more in the spark plug hole. Since there is no visible oil leakage from the outside, it can only be detected when replacing the spark plug. Pulling out the ignition coil and seeing oil on it, it must be that the valve cover gasket is leaking oil and needs to be replaced in a timely manner. If left untreated, the ignition coil will remain immersed in engine oil and its lifespan will be affected. The spark plug is also surrounded by oil, which blocks the close contact between the ignition coil and the spark plug, forming an oil film between them, affecting ignition performance and causing a feeling of decreased power when driving. In severe cases, it can cause a short circuit at the ignition coil, leading to the breakdown of the spark plug and complete damage. So the valve cover gasket must be replaced promptly if it leaks oil towards the spark plug.

If there is a lot of oil in the spark plug hole, do not remove the spark plug hastily. Clean the oil first before removing it. Because after removing the spark plug, the oil inside will flow into the cylinder, first causing carbon deposits in the cylinder, as the oil cannot burn completely, leaving behind a large amount of impurities. Secondly, if there is a lot of oil, there is also a risk of knocking the valve. In reality, situations where there is a lot of oil are very rare. Most cars only have a small amount of oil inside. If the amount of oil is small, it can be removed directly. A small amount of oil entering the cylinder does not have a significant impact. Because if the amount of oil is low, it is not easy to clean.

Some people also found oil on the threads of spark plugs when replacing them, but not elsewhere. This is basically also caused by oil leakage from the valve cover gasket, but the amount of oil is very small and accumulates at the bottom of the spark plug hole, and the ignition coil just can't reach it. As the spark plug is removed, the oil will continue to flow downwards and onto the threads of the spark plug. This situation can be ignored for now, continue to use it for a period of time, and then check for any oil leakage. If the oil leakage is obvious, replace it.

From: WONDEE Autoparts

2024-3-7