Nissan Patrol 4x4 (Africa)

Looks like the knocking in my engine was caused by a failed glow plug. Has anyone seen this before?

That happens when the cold start circuit stays on and the glowplugs stay on heat..the tip of the glow plug melts of and falls on piston.....
welldone for picking up that noise so early..could have been worse..

Wow.... never seen that before !!!

That could have been a major disaster had it jammed up a valve !!

Crazy hey!

Well spotted before catastrophic failure...

In both 3.0 engines where I had the cylinder head off these same marks were on the pistons. I think it's more common than we think.
The tip that breaks off is not the hardest material in the world and eventually gets smashed to pieces in a very short time period without causing real damage to the piston or head.

it seems like on this engine it is already out the exhaust within only a couple or revolutions or did you find the glow plug tip in there?

Sorry for the slow reply... There was quite a big piece of the glow plug missing, and that seemed to be partially embedded in the piston. The noise was very obvious, a very loud rattle, so carrying on was not really an option. But it still took a very long time to work out what the problem was.

Not entirely sure why there was such a noise, but that piston and its rings were in much worse shape than the other three, so maybe there had been some detonation issues. Or maybe it was just from poor combustion when cold.

Apparently the sign of a glow plug failure is a puff of smoke when starting cold. So look out for that.

Happy you found it ....my 4.2 always makes black smoke ...can take that to the bank ....