[nickd]

John, I notice some extra info on here from the rennlist thread. The hammer marks on the cover would worry me. I would hope that a new cap from Porsche wouldn't be too expensive. Though maybe the incorrect use of a sealant on the o-ring is the real problem.

I don't remember anymore from when I replaced this o-ring, and I wasn't sure from the descriptions above- can you feel any kind of lip inside the o-ring bore where the case halves meet?

For another data point on sealants, I followed Henry's recommendations on my 964 rebuild and it's 100% leak free (except the nose bearing/ims area) after a few years, around 10k miles, and hundreds of autocross runs. I didn't split the case but I did replace the through bolt o-rings one at a time. Many of them came out mangled. The motor had about 70k miles and had never been opened before, so the factory must have destroyed a few o-rings during the original assembly. It had a number of leaks from the through bolts. I would put dc55 on my pancakes if I could. Love that stuff. Good luck John.