If you're a team lead then being open is part of your job description, if you're not a team lead but want to be one then being open will help you get there. Sharing knowledge isn't just for team leads and senior developers, it is for everyone and should be part of the team mind-set. Sharing your knowledge with other people makes your team and organisation more successful, it makes you more successful and helps you build relationships with others. I cannot recommend more highly sharing your knowledge openly with others.
Stop time wasters and protect your knowledge sharing culture
As a senior engineer or a technical lead you need to be there for your colleagues from mentoring to helping them out with obscure problems. If done right it can make your team a lot more productive, can help your career by showing management that you are an effective leader and is generally rewarding. If done wrong it will harm your productivity and spoil junior colleagues by creating dependence behaviour.