It's the threads that leak. I think they put some crap around the threads like sealant. When you break the seal, they leak.

 

yea there's some factory goop on mine when i took them out to rebuild. that's why i ordered the goop that's coated on the speedbleeders.

i think there is a loctite that will work to seal the bleeder screws, but i can't remember which one. it's brake fluid proof!

 

Dam im gonna need another helper haha. The left one has corroded white stuff all around the top which is kinda weird, id figure they would all leak. I know that its a tapered bleeder and tapered caliper that once its tight they seal but oh well. Just got home and checked and nothings leaking rear pedal still feels stiff so thats good.