oil leak from injector 3306 in D7G

Early days on this but the injectors in our D7G seem to be leaking oil... Really seems like oil (smell, colour, feel) not diesel. Coming from high up as in at the base of the flare nut for the injector line. To test, while it was still warm I cleaned one injector off with a rag then gave it a little run (walked it up a hill for a few minutes), had a look and there was some seapage from around the nut, and I even saw tiny air bubbles coming out - not many, maybe one every 10 seconds.

It's running nicely, no missing, good power. Does use a bit of oil and the head is covered - like it's a leaking rocker cover gasket (which I suspected at first as did the valves recently). Anyone heard of something like this or know if there's an oil gallery sealed off by the injector or pre-com.?? Have the manual and not finding much so far...

Don't see any way it can be engine oil from that source, the rocker cover gasket is the most likely suspect for sure.

Undo the pipe nut and see if there is a flat collar that slips over the injector pipe and butts up against the back of the bullnose on the end of the injector pipe. The collars are easily split if you over-tighten the injector pipe nut.
The 'O' ring (small one) that goes under the nut has a steel insert in it. A normal 'O' ring is not suitable.
The Cat part number for the 'O' ring is 6F-1069 and the nut tension is 30 foot pounds.

The O ring that goes under the injector nozzle hold down nut is Cat part number 5B-3718. The tension of the injector nozzle hold down nut is 105 foot pounds. Over-tension will distort the injector nozzle

If there was any defect (cracking) in the pre-combustion chamber, the cooling system would be getting pressurized.

The part numbers quoted may be superseded.

...yeah .. i reckon grumpy's right...

...taught him everything i know y'know : :

Ya not wrong Phil ..... and I still know bugger all
Change of address coming up soon ..... Basra, IRAQ

thanks guys. Thinking I might replace the rocker cover gasket first - think it might actually be both at the moment. Might get those washers etc. ordered before touching the pipes in case I can't get it back together. Just surprised it's running so well with a leak...

Those old 3306 engines will run sweet as a nut even when they are totally worn out .... almost impossible to kill. Had a few out on the rigs running generators 1500 rpm for some, 1800 rpm for some ..... 50,000 hours plus before any major overhauls done. It's a pity they still don't make them.