Excessive oil deposits on #1 spark plug.

Discussion in 'Troubleshooting & Diagnosis' started by 78BBODY, Sep 6, 2021.

  1. 78BBODY

    78BBODY Member

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    Hey all, new here. Seem to find a lot of helpful tips here so why not join and ask about my own issue

    I recently bought a car with a Chevy 350, and noticed when doing a tune up, number 1 spark plug had excessive amounts of what I assume is oil buildup. I changed all plugs for assurance, but after about 200km, I noticed it started to miss and ping a bit. Pulled number 1 again and sure enough, buildup.

    I bought a catch can to see if that helped with oil getting into the cylinder, but seems that isn't helping. Haven't performed a compression test yet but will soon.

    Unfortunately, I have no history on this engine. It has basic bolt-ons; carb, intake and headers, but aside from that I know nothing about internals.

    My question is, why is this happening to cylinder 1 and not the others?

    Thank you.

    Jon 20210502_121254.jpg
     
  2. Gary S

    Gary S Administrator Lifetime Gold Member

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    That might not be oil. Oil is really black and wet on a plug. This looks more brown and dry. It could possibly be a coolant leak.
     
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  3. 78BBODY

    78BBODY Member

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    Oh boy, I never even thought of that. Looking up some photos and it does seem similar to a coolant leak.

    Is there anyway to test this without removing the head?
     
  4. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

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    Doesn’t look like oil to me either.

    If it’s coolant, hopefully it’s leaking at the intake gasket instead of the head gasket.

    The intake gasket is a much easier fix.

    What type/color of coolant are you using?
     
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  5. mallard

    mallard Veteran Member

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    Do you have any steamy white exhaust fumes? You could also try a pressure test on the cooling system and see if there’s a pressure loss and/or some hissing sound when you take the oil filler cap off. Or perhaps is there some oil frothyness? Or try a pressure test with that plug out?
     
  6. 78BBODY

    78BBODY Member

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    I'm hopeful its the intake gasket as well. Next time I get a chance I'll pull it and replace them.

    I did notice when I bought the car, the intake bolts were loose, and a liquid had pooled on top of the intake. Could this have ruined the gaskets over time?

    I'm using regular coolant/antifreeze.
     
  7. 78BBODY

    78BBODY Member

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    No exhaust fumes other than at startup until it warms up.

    A pressure test would be a good idea. Are there specific tools I would need for that?

    Oil quality seems okay on dipstick, not sure of any other way to check without taking things apart.
     
  8. COPO

    COPO Veteran Member Lifetime Gold Member

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    Usually a fuel additive will create a different colour on the plugs. If its a coolant leak then the plug would be clean as a whistle.
     
  9. mallard

    mallard Veteran Member

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    You’d need to buy a cooling system pressure tester. You can get them at any store that sells automotive stuff.
     
  10. 78BBODY

    78BBODY Member

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    I do run Shell V-power, that according to Shell has 7x the minimum requirements of cleaning agents. Other than that, I add nothing to the tank.
     

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