@SteveKickert Before I was mowing with my MX5 and the temp gage was almost in the red, I had to keep turning off the a/c to keep it out of the red. JDLTG linked my post about finding the latches to remove the grill. When I did that the lower part of the radiator (can't see from the top) was coated/covered in dust and I couldn't see the fins. One of the pics in the post you can see my brother with an air nozzle blowing it out.
Check your overflow tank just in case like SRG said.
For others that don't have a 3R tractor there is no screen in front of the radiator you can pull out to clean.
After cleaning it I haven't had it get near the red on the gage. Earlier in this week I was raking hay and straw for a couple of days and the a/c was on the whole time. It was in the 80s with high humidity and I never got hot in the cab, I would adjust the vents to blow on me or away if I wanted to be cooler or not.
@myrna I don't think the range he was mowing in would cause his tractor to overheat, it could cause it to slow down or stall but not over heat. I was pulled two kicker wagons with my 3039R in B range at about 8mph, the wagons had about 135 bales of straw each. Not sure what the wagons and straw weighed (a lot) but I could have pulled in C a little faster if the dirt road wasn't so rough.