Fixing Oil-Filled Spark Plug Wells

Does This Problem Need an Immediate Solution?

Spark Plug

When a spark plug well fills with oil, it means that the O-ring that seals the spark plug well and keeps oil out has deteriorated and started leaking, though the leak can sometimes be fixed by tightening the valve cover bolts. However, more often than not, the valve cover gasket and well seals will need to be replaced if oil is in the spark plug wells.

An untreated problem like this will cause the spark plug boot to swell and lead to a misfire in the engine, which will certainly hurt engine performance and might even possibly cause an engine fire to start; it's important to get this issue fixed or fix it yourself as soon as you discover it to avoid possible damage to yourself or your vehicle.

Classic cars are especially prone to oil leaks, so it's important to know what to look for when assessing where a leak is coming from, though the best place to start is usually by checking whether or not the valve covers need to be replaced.

When to Replace Your Spark Plug Wells

It's important to keep in mind that it's not always entirely necessary to replace your spark plug wells entirely. Oftentimes just replacing parts of the valve, especially the cover, will suffice for fixing an oil-filled spark plug well.

If the gasket is not sealed around the spark plug well, it is likely to leak oil into that area, which will pool and eventually cause problems for the engine. Although this is the most common cause of the issue, a failing piston or worn valve guides can also cause this issue, so your mechanic should investigate those as well.

Ideally, you or a mechanic should check your valve cover gaskets, O-ring seals, pistons, piston compression rings, and valve guides to rule out any possibility of further damage than the surface-level valve seal.

It's critical to treat this issue as soon as possible to avoid the complications it might cause, which could include fatal damage to the engine. Oil in a spark plug can do extensive damage to different areas of the motor, such as warping or breaking the valves and pistons or destroying the head gasket which could lead to an engine fire.

Other Issues that Effect Spark Plug Output

Although oil-filled spark plug wells are a common issue, there are a variety of different factors that can contribute to misfires in the engine, especially as they relate to the spark plugs and their associated parts.

The spark plug wires, for instance, can break down in a variety of ways that will cause a vehicle's Check Engine light to come on. You should inspect your spark plug wires for breaks in the insulation regularly as this can lead to arcing and a weak spark or no spark at all, which ultimately affects your gas mileage.

Oftentimes, this will require replacing your spark plug wires, which should happen every 30,000 miles regardless of engine performance — if you're changing the spark plugs, consider changing the wires at the same time.