Just went through this ordeal with one at work. 135, first one I've had to deal with.
Screen was clean. Customer said he cleans the radiator religiously. First inspection of the tractor and he's right. He does. It was clean. Externally. Down deep between the fins looked ok too. Out of a suspicion, I ran a garden hose in behind the radiator, kind of between teh fan blades, forcing water through from the back side. Guess what? Got about 3 lbs of dirt out of it. BTW it "looked" great-visually. Gave it a good cleaning and returned it....says it works fine now.
You've got a a/c condenser, an oil cooler, intercooler and then the radiator. If any one of them is getting restricted with dirt, it'll restrict air to the radiator-and what air the radiator does get will be warmer than it needs to be (because the core in front of it will be hotter than it needs to be). So everything has to be nice & clean on them. This has been a challenge since liquid cooling was first used on tractors...way back in the 1700's....wait...or was it 1800's?
Start there...clean from the backside, with a water hose only. Do not use a power washer as it'll damage the fins.
When's the last time the coolant was changed? It should be changed every so often per owner & service manuals. Neglecting to do it will result in bad things. Coolant, brake fluid, and differentials are the 3 most neglected parts of most vehicles...and a cause for many, MANY failures.
