Hi all,

I finally decided to tackle the oil leak on my '87 XJ12, so I took the intake manifolds off with the intention of replacing the cam cover gaskets along with aluminum half moon seals. However from looking at the area, it now seems to me more like the tappet block seal leaking. As I'm not so experienced, I would greatly appreciate some help with identifying if that's the case - took some pictures which are down below.

Thanks,
Dan

 

Looks suspect,

BUT, in all my V12 chariots, that has always been from elsewhere. Oil seepage/spray back on a V12 is not easy to find the source.

Greg in France had leakage there on his, and did an RTV fix without removing all that stuff.

He will slide in when the planets align better, and give you the good words.

Too late now, but I would have washed that down thoroughly, and ran the engine, and look again, but hindsight is fabulous of course.

 

I would do the cam cover gaskets and half moons, now you are in there, silly not to, and there is definitely some weeping from them.
My tappet blocks were weeping far more than yours seem to be. Also, from the pics, it looks like there is some sort of gunk along the join. In my case I did this:
Cleaned up the entire tappet block to head join area with white spirit.
With a sharp flat-ended screwdriver scrape out anything in the join (that black bead in the join visible in your case).
With a wire brush in a drill roughen up the area both sides of the seam, ALL round the entire seam in- and outside of the V, then use coarse sandpaper to do more.
Re-clean with white spirit or carby cleaner.
Buy some hi-temp silicone (eg Permatex copper hi temp gasket stuff) and apply all round the seam, pushing it into the roughened surfaces with a finger.
i did this 10 years ago and bone dry since. Completely invisible once the induction is back on. You can no doubt make a neater job than i did, but here it is:

 

That would've been smart! I'll try to save that tip for the future.


Greg, thank you for the instructions. I was definitely going to do at least the cam cover gaskets and half moon seals of course. Sounds like a solid plan of attack to adress the tappet blocks this way though! Without having to pull the cams and all that. I actually recall having seen your solution in some other thread before, but I wouldn't remember it, so thank you again!