Yes, what happens when the senior engineer leaves the company, having never shared his or her knowledge? It sounds like you are trying to address issues during

Yes, what happens when the senior engineer leaves the company, having never shared his or her knowledge? It sounds like you are trying to address issues during mentoring that should have been addressed during the hiring process. In my experience, all the juniors I've worked with come in with the idea that they can solve every single issue themselves, and part of my job is to show them how wasteful that is, that a simple question can save the whole team days if not weeks worth of time. If someone walked through the door who is not enthusiastic about solving technical issues themselves...your hiring process needs work.