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  1. #1

    Default Oil in the cylinder???

    I was just changing the spark plugs in my 03 Trailblazer EXT and the first three plugs I changed, two of the cylinders were full of oil. I am kind of scared to see what the other three look like. To what extent is the damage or should I just get a rebuilt motor?

  2. #2


    When you say "full of oil" do you mean you have fouled plugs or do the cylinders actually have oil in them.
    Either way oil in the cylinders doesnt mean a total rebuild or replacement of the engine, you need to find out if the oil is from worn rings/cylinder walls or bad seals on the valves. Another possibility could be head gasket damage allowing leak through, but thats less likely.
    You should probably start diagnosysing by doing pressure tests.

  3. Thanks RonaldJohn thanked for this post
  4. #3


    When I took the coil off, the spark plugs had a little oil around them, then when I took the spark plug out, the cylinder was full of oil...

  5. #4


    The plugs, on that engine, are in wells in the valve cover. Oil in those wells is a very common problem. New valve cover gaskets will solve the problem.

    Water (rain/splashed) is also a common problem with that engine, the hood has a gasket that should seal the rear of the hood and keep the engine dry. It does not work very well, letting the plugs (#4 in particular) get wet. You may find water in #4.

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

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