I dont know why it keeps leaking after you have resealed but i would highly recommend a toyota silicone that is black in color(sorry dont have part number but most toyota dealers should know.. they have black and grey(yamabond type)).

I dont know what the stuff is but i used it when working on toyotas and it was virtual leak proof. the stuff is amazing at sealing up engines/transmissions/diffs(basically holds in any lube). And if you get it on your hands, plan on having black hands for about a week. Stuff sticks to EVERYTHING.