Causes of Oil on Spark Plug Threads

You should have more curiosity about the engine components and their failure symptoms and causes. In that regard, we have discussed the Causes of Oil on Spark Plug Threads.

Regular maintenance gives an indication that spark plugs have an oil on their threads (wells). If you notice this symptom, It should be clearly diagnosed.

There are many possible Reasons for Oil on Spark Plug Threads. You will get an Idea what exactly to do further by understanding these causes.

Reasons / Causes of Oil on Spark Plug Threads –

1 – Head Gasket Failure

Blown or Damaged head gasket is also one of the reasons of oil on Spark plug threads. Because, With damaged head gasket, oil or coolant comes into the combustion chamber which further gets stuck to the spark plug wells or threads.

We can notice this cause with exhaust smoke because of Either coolant or Oil gets burnt into combustion chamber. Gasket should be replaced as early as possible.

2 – O-Ring Leakage

If Spark plug gasket is not used then there is a usage of O-Rings on the spark plugs. Spark Plug O-Rings separates the oil from the spark plugs. O-Ring helps to protect the other side of the spark plug. If you found the oil on Spark plugs then there might be the reason of leaky O – Ring.

3 – Worn Valve Guides

Valve guides maintain the position of intake and exhaust valves also they provide the sealing to keep oil away from the combustion chamber. If these valve guides / seals gets damaged then oil comes into combustion chamber which further causes the oil on Spark plug threads.

4 – Damaged Piston and Piston Rings

Piston rings specially compression rings are responsible for keeping the oil away from combustion chamber. If these compression rings gets failed then there will be a path for oil to enter into chamber which further causes the oil on Spark plug threads.

Damaged / Worn piston is also responsible for oil coming into the combustion chamber. So You should be aware about this cause of piston and it’s rings failure.

5 – Valve Cover Gasket Leakage

Valve cover Gaskets, if gets damaged then surely spark plugs could be affected by oil. This type of Gasket is cheap but labour cost is high for that replacement.

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