If this is a leak out of the cable's hole? There is an o-ring missing at that area. See if the old cable has that o-ring at the hex part, or say, look in between the hex and the threads of the cable. Is there an o-ring there?
Other leak is the cover gasket. If you use some oil resistant silicone around the old gasket, maybe it will hold. If not, install a new (dry) gasket on both [dry] metal surfaces.