We have a JD 772, I did a water pump gasket on it. I also found that the belt was bad replaced the belt. After it ran for 5-6 hours the belt started to make nosie, I sprayed the idlers with wd40 found one bad replaced. 2 hours later same thing replaced the other two. Know it still makes nosie. I sprayed some belt dressing stuff on the belt it gose away for about 10 min then comes back. The alternator pully is good nothing changes when you spray that. Any ideas?
I would take the serpentine belt off the machine and wash it with brake kleener, and do the same with the pulleys. Also count the ribs on the belt and the 'V' s on the pulleys, many times I have seen the wrong belt installed and making noise from mismatched grooves.