If you tell him you don't need him, and he goes away, I don't think you'll be able to pick him up. He only joins for a short quest anyway, you can't use him inside the volcano.
I had already rescued him once before in the first temple that had lizard men. He was stuck in one of the prison cells. After I released him, he sat outside the northeast temple near the bottom of the waterfall. Maybe you have to release him twice to get him to help you?