I bought a used but rebuilt T3/T4 jourbal bearing turbo from a member here. Well the turbo leaked a tiny bit of oil basically since it was installed. Now theres oil in the cold side piping(quite a bit of it).
What could cause the turbo to leak like this, and what do i need to do to fix it?

 

Most likely time for a rebuild if your oil return line is clocked properly and is free flowing.