Oil leak from spark plug recess

[afpj]

well, another oil leak post...sorry. Our 02 yuk with 187 k miles has been losing oil, about 1 qt per 3000 miles. No smoke from exhaust. Coolant fine. Some oil collection at oil drain plug area, passenger side. I’ve traced at least some of it to the spark plug recessses on drivers side the 2 closest to firewall. It seems like it’s leaking from around the plug, using a fiber optic camera. With plugs removed, there’s no fouling, but there’s oil on the threads. Is the head cracked at the plug? The plugs thread easily, and seem to tighten just fine to 11 ft lbs ( torque spec that I found). I cannot se ant cracked with the camera with plugs out. Anyone have any ideas? Thanks in advance for any thoughts on this.
Happy thanksgiving! I’m thankful this rig lasted this long.

 

[SnowDrifter]

Sounds like valve cover gaskets TBH. Barring a cracked head, that's the only area it could come from.

If its particularly elusive, a good engine bay clean combined with some UV dye and a black light will help you find the source of the leak

 

[afpj]

Did the dye, and it’s not dripping from the valve covers. I can only trace the dye with the black light to the spark plug recess ( can see it without dye too but that orange glow makes it a bit more obvious), and using the inspection camera, see the oil in the plug recess. I can’t find a way to actually look directly into the recess with the light to see where in the recess it’s coming from ( the access angle is wrong, and even though my wife says I’m a pinhead, I cannot get my noggin in far enough to get line of sight with a black light). A mirror wasn’t helpful either. Can’t figure how to use inspection camera with black light source. When looking with the camera at the plug hole, it’s clean around the bottom mating surface, as if that’s the path the oil is taking....everything else around the plug hole is grimy. Well, I cleaned the recess as best I could to insure the plug mating surface is clean 360 around, and put back together...maybe the plug was put in and tightened with grime so the mating surface was uneven. Don’t know how close the oil jacket is to the plug recess area, but the crack head idea is looming. Thanks for the suggestion. May your Thanksgiving be blessed.

 

[Scottydoggs]

gm has always said that a qt being burned off is somewhat normal after you pass 100,000 miles. seen it happen on both my trucks i bought new from the dealer. hit 100,000 miles like magic started to eat a qt by 3,000 miles, and almost every accessory on the front of the engine went bad. both trucks same deal, both gmc's, one was a 97 3500, the other a 03 2500 HD. so not even the same engine family really. neither of these trucks has a soft life either, both did about 3000 miles a month ( and a oil change per month) and both plowed snow. the 97 had 175k on in it 5 years.