Mahindra tractor 4500 2wd

What can I check to see why my tractor may be getting hot too soon. So far it appear it runs hotter when I am bush hogging. I have a Mahindra 4500, I am cutting grass with a 6' red ANDY bush hog. I do have my bush hog set real low to the ground, because it cuts grass low like a walk behind push lawnmower. because my 6' bush mower is cutting so low be causing my PTO to run the tractor hot fast. This bush hog I got must also be a grass muncher also, because it not only cuts the grass but it munches the grass also. When I say it running hot, the temp needle goes to the middle of the temp scale, after 20mins of cutting. I removed/clean the stream in front of the radiator, still run hot after 15 to 20 mins. This tractor model do not have a fan in front of the radiator. What else can I look for that may be causing this quick overheating??? Is my 6' Andy bush hog too big for this tractor????