When I did the clutch recently on 300tdi engine I replaced the rear crank oil seal and gasket with genuine LR parts (might as well have fitted britpart!). The old one seeped a tiny amount of oil, like half a teaspoon every few thousand miles. But now with the new one its a proper oil leak. I fitted as as per workshop manual, cleaned faces, gasket fitted right way around, used the ring guide thing, torqued up etc ....so what went wrong? I am going to have to whip engine out again and replace it but I do not want to make what ever mistake I made again.... tips ?