I was changing a spark plug out on a 2000 Ford Expedition with a 5.4L Triton, with the coils on the plugs (COP), and I'm worried about how dirty it was. I was being as careful as possible, but I know a little bit of dry grease fell into the combustion chamber. It's difficult for me to know how much. I can guess at maybe 3 to 5 pinches, or to express it another way, maybe about 1 mL. I know this can potentially scratch at the chamber wall, what I don't know is, since I've driven it since then, does grease eventually burn to ash and emit out of the valve, or will I need to employ some method of cleaning it out? It seems like with COP setups, a little bit of grease falling in can be fairly common, but I suppose I could be wrong.

  • If it is big try blowing it out, if you can't blow it out, forget about it. That's what your mechanic would do. :) Feb 24, 2018 at 0:33
  • The stuff you get into your engine by crankcase ventilation over the lifetime of the engine is far more detrimental. It will eat up your little grease right away. I wouldn't worry about it. Carefulness is more of a concern when creating a clean area for a proper seal of the plug.
    – Bart
    Feb 24, 2018 at 16:00

1 Answer 1


The only real way to get the debris out without it causing any damage at all would be to remove the cyl head. Its the extreme way but the only definite way to know that the bore, rings & valves etc won't be subject to it.

Second best would be to leave the spark plug out, rotate that cylinder so its approaching top dead centre if required and see if there's any possibility of fishing the culprit out with a grabber type tool etc or blowing it out with compressed air.

In reality though as you've driven the vehicle, and I'm assuming its still running ok without misfiring etc, this bit of dry grease is unlikely to be a problem. If it was going to be problematic a bit of dry grease may have perhaps just held the exhaust valve open temporarily before being squashed, burnt and any remains blown out of the exhaust valve.

If however you're still concerned, do a compression check on that cylinder just to make sure everything is as it should be.


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