Either I don't have this sort of noise on mine or I am simply not hearing it. The only noise I have is an irritating rattle from inside the cab - rear left somewhere which I have not narrowed down yet.
A little rattle ain't bad for a tractor. About 25 hours on mine now and zero complaints.
I will take a look for the bypass valve if I can tomorrow. Unfortunately I fly out of the country for a week and a half so I'm not sure if I will be able to give you an answer right away.