I've never bathed my snakes so I can't be much help there, but I would say luke-warm, not deep water.
With the noise, listen very carefull to see where it is coming from. When snakes have respiratory infection they often make clicking sounds when they breath, which they shouldn't be doing with normal health. Other signs of respiratory infection to look for are keeping the head up, gaping, breathing with the mouth open, puffy throat, blowing bubbles or seeing mucous around the mouth.
Of course, he could just be stressed at being handled since he is new, and be trying to scare you off. Try and see if he makes the noise when you aren't holding him.
Investigate further and come back with any more questions,
Skye