Stating the obvious, but have you checked all the simple stuff? I don't know about the pressures and all.
I got mine used and the AC radiator was packed with schmoo. I was blowing it out with a leaf blower, but could only bush hog for 45 minutes or an hour before the compressor would stop coming on. I got 2 fancy air wands and a water wand. Made a huge difference to clean it within an inch of its life.
I bush hogged one field for the first time this year today and ran for over 3 hours before it got clogged with seeds. Was still running though. I've thought about fitting an extra screen in front of the auxiliary radiators to make cleaning easier and hopefully work longer between cleaning. Maybe it is Kioti's way of telling me to cut the field more than once or twice a year - LOL.