Tan-colored goop around spark plug


#1

1996 Chevy S-10, 2.2L I4, 61K miles



I was installing a new set of spark plugs (OEM AC-Delco’s), and I had an oddity when removing one. I went to remove the plug in cylinder #3 and it was a bit hard to turn, so I sprayed some PB Blaster down into the tube to let it work the old plug loose.



When I withdrew the socket, it was coated in this tan goop that was very sticky like undried RTV. I got the plug out, and the exposed end of it was also covered in this stuff (not where the plug wire connects, just around the plug’s ceramic insulation, as if someone had poured this stuff around the plug with the wire in place). I installed the new plug and the engine started right up, no problems and no funny noises.



Anyone have some idea of what this gunk is, and why the spark plug tube was filled with it?


#2

That sounds like a water and oil mix that has been reheated a few times.

If there is oil in the plug valley it could be from a leaking valve cover gasket and the water could either be from collective condensation or from driving during a rain.


#3

That’s a thought, but I can guarantee that the valve cover gasket is not leaking now as the engine doesn’t lose a drop of oil between changes. Perhaps once before I got it, it did leak…


#4

I think that such a small leak would be undetectable in terms of the oil level or amount of recovered oil. Would you be able to tell if a couple of tablespoons of oil were missing?


#5

When you say “exposed end” do you mean the electrode, or simply the area where the insulator engages with the nut?, thus external to the cyclinder.

If internal… does not sound too familiar. If external only, then I’d say oil/coolant leaking into the plug hole from somewhere, coudl just get blown in there from the rad cap or a leaky hose joint.