So, I've finished the 2nd tensioner on the right side of the engine. Everything went great. Clean as a whistle after 36000 miles, and the right tensioner has no cracks. Put back together and moved on to the left side.

Happy happy no problem with the oil dip stick or the lower left rear cam cover bolt on the left bank.
However,(you knew this was coming right?) opening the left side coil cover and I noticed a light dusting of corrosion on the coils getting heavier from front to back.
Then I noticed that each of 3 coil/spark tubes had light dusting of a brown non-ferrous material on it. I pulled the first three, not an issue. The last, left rear coil/spark tube came out with what I can only describe as a coating of hardened mud on it about halfway down and to the bottom. I thought maybe someone had power washed the engine and gotten some water and debris in the tube and it hardened and dried. Magnet showed not rust, but looked like hardened mud. Some build up in the base of the tube, and the plug appeared not to have been fully seated with the washer caught on the threads(I reset the washer). Spark plug appeared as running slightly rich. I was confused as to what to do beyond this. Engine ran great with no codes before I began the tensioner replacement. Have not yet restarted. Torn between cleaning out the plug tube and changing the plug on the rear left bank and just leaving(letting) sleeping dogs lay(lie? I never know the appropriate grammar rule. The nuns beat me regularly, a GREAT educational tool, but nothing ever stuck.) and letting the plug find its way in and leave the mud.
Has anyone seen this before? My fear has run the gamut from head gasket to block or cooling passage filler or some type of stop-leak.
But if there was a catastrophic failure it would not run as well as it had prior to the tensioner teardown. And that there would be several codes appearing. Of course if I screwed the pooch on the tensioner replacement that may be ancient history.
I know that I tend to be talkative(writeative?/wordy) in these posts, but green eyes stopped listening/talking to me about the Jaguar days ago except to ask when can she drive it. So you forum members get to bear the burden of my posts.
Thanks in advance,
Dennis

 

Could that be oil residue from the cam cover seals leaking?

 

RJ,
I suppose that could be the case. I did see some oil in the other tubes(minimal) but I have never seen this type of residue from cooked oil before. The seals are in need of replacing.
I wish I knew how to post pics from my phone. I would send them to the forum for others to see.
Thanks for the reply,
Dennis