twoturbos

Hi, I have rebuilt my xr6t engine top to bottom, slotted in and within 100k engine bleeding oil rocker box, front cover, sump????. Got advice from local engine builder to coat all gaskets in permatex gasket sealant. Engine out again covers off clean up coat reassemble. Have run now for 700ks and now r/h front of sump leaking. I have done all by the book throughout build. This has got me stumped & looking like engine out again. Any ideas will be muchly appreciated. T