Hi,Can someone enlighten me on their methods of verifying where oil leaks are coming from.I have one now that leaks from the right rear of engine,this is a 6 liter,and comes out around the back of the starter where the rear engine cover and block meet.This truck has already been worked on 4 times for leak concern.The other tech replaced rear main seal,valve cover gaskets ,twice,and replaced glow plug harnesses.I contacted hotline and they suggested starting at top.I replaced hpop seal,turbo return pipe orings and oil cooler gasket.This leak is vey slow and takes several miles to show up.I am new at this,and need some expert advise.How would you determine the difference of a t-joint leak as to say a block leak?I have cleaned this engine very well and try to observe leak,but cannot find source.Thanks for any help.